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diff --git a/PdfFileTransformer/PyPDF2/xmp.py b/PdfFileTransformer/PyPDF2/xmp.py
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+import re
+import datetime
+import decimal
+from .generic import PdfObject
+from xml.dom import getDOMImplementation
+from xml.dom.minidom import parseString
+from .utils import u_
+
+RDF_NAMESPACE = "http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+DC_NAMESPACE = "http://purl.org/dc/elements/1.1/"
+XMP_NAMESPACE = "http://ns.adobe.com/xap/1.0/"
+PDF_NAMESPACE = "http://ns.adobe.com/pdf/1.3/"
+XMPMM_NAMESPACE = "http://ns.adobe.com/xap/1.0/mm/"
+
+# What is the PDFX namespace, you might ask?  I might ask that too.  It's
+# a completely undocumented namespace used to place "custom metadata"
+# properties, which are arbitrary metadata properties with no semantic or
+# documented meaning.  Elements in the namespace are key/value-style storage,
+# where the element name is the key and the content is the value.  The keys
+# are transformed into valid XML identifiers by substituting an invalid
+# identifier character with \u2182 followed by the unicode hex ID of the
+# original character.  A key like "my car" is therefore "my\u21820020car".
+#
+# \u2182, in case you're wondering, is the unicode character
+# \u{ROMAN NUMERAL TEN THOUSAND}, a straightforward and obvious choice for
+# escaping characters.
+#
+# Intentional users of the pdfx namespace should be shot on sight.  A
+# custom data schema and sensical XML elements could be used instead, as is
+# suggested by Adobe's own documentation on XMP (under "Extensibility of
+# Schemas").
+#
+# Information presented here on the /pdfx/ schema is a result of limited
+# reverse engineering, and does not constitute a full specification.
+PDFX_NAMESPACE = "http://ns.adobe.com/pdfx/1.3/"
+
+iso8601 = re.compile("""
+        (?P<year>[0-9]{4})
+        (-
+            (?P<month>[0-9]{2})
+            (-
+                (?P<day>[0-9]+)
+                (T
+                    (?P<hour>[0-9]{2}):
+                    (?P<minute>[0-9]{2})
+                    (:(?P<second>[0-9]{2}(.[0-9]+)?))?
+                    (?P<tzd>Z|[-+][0-9]{2}:[0-9]{2})
+                )?
+            )?
+        )?
+        """, re.VERBOSE)
+
+
+class XmpInformation(PdfObject):
+    """
+    An object that represents Adobe XMP metadata.
+    Usually accessed by :meth:`getXmpMetadata()<PyPDF2.PdfFileReader.getXmpMetadata>`
+    """
+
+    def __init__(self, stream):
+        self.stream = stream
+        docRoot = parseString(self.stream.getData())
+        self.rdfRoot = docRoot.getElementsByTagNameNS(RDF_NAMESPACE, "RDF")[0]
+        self.cache = {}
+
+    def writeToStream(self, stream, encryption_key):
+        self.stream.writeToStream(stream, encryption_key)
+
+    def getElement(self, aboutUri, namespace, name):
+        for desc in self.rdfRoot.getElementsByTagNameNS(RDF_NAMESPACE, "Description"):
+            if desc.getAttributeNS(RDF_NAMESPACE, "about") == aboutUri:
+                attr = desc.getAttributeNodeNS(namespace, name)
+                if attr != None:
+                    yield attr
+                for element in desc.getElementsByTagNameNS(namespace, name):
+                    yield element
+
+    def getNodesInNamespace(self, aboutUri, namespace):
+        for desc in self.rdfRoot.getElementsByTagNameNS(RDF_NAMESPACE, "Description"):
+            if desc.getAttributeNS(RDF_NAMESPACE, "about") == aboutUri:
+                for i in range(desc.attributes.length):
+                    attr = desc.attributes.item(i)
+                    if attr.namespaceURI == namespace:
+                        yield attr
+                for child in desc.childNodes:
+                    if child.namespaceURI == namespace:
+                        yield child
+
+    def _getText(self, element):
+        text = ""
+        for child in element.childNodes:
+            if child.nodeType == child.TEXT_NODE:
+                text += child.data
+        return text
+
+    def _converter_string(value):
+        return value
+
+    def _converter_date(value):
+        m = iso8601.match(value)
+        year = int(m.group("year"))
+        month = int(m.group("month") or "1")
+        day = int(m.group("day") or "1")
+        hour = int(m.group("hour") or "0")
+        minute = int(m.group("minute") or "0")
+        second = decimal.Decimal(m.group("second") or "0")
+        seconds = second.to_integral(decimal.ROUND_FLOOR)
+        milliseconds = (second - seconds) * 1000000
+        tzd = m.group("tzd") or "Z"
+        dt = datetime.datetime(year, month, day, hour, minute, seconds, milliseconds)
+        if tzd != "Z":
+            tzd_hours, tzd_minutes = [int(x) for x in tzd.split(":")]
+            tzd_hours *= -1
+            if tzd_hours < 0:
+                tzd_minutes *= -1
+            dt = dt + datetime.timedelta(hours=tzd_hours, minutes=tzd_minutes)
+        return dt
+    _test_converter_date = staticmethod(_converter_date)
+
+    def _getter_bag(namespace, name, converter):
+        def get(self):
+            cached = self.cache.get(namespace, {}).get(name)
+            if cached:
+                return cached
+            retval = []
+            for element in self.getElement("", namespace, name):
+                bags = element.getElementsByTagNameNS(RDF_NAMESPACE, "Bag")
+                if len(bags):
+                    for bag in bags:
+                        for item in bag.getElementsByTagNameNS(RDF_NAMESPACE, "li"):
+                            value = self._getText(item)
+                            value = converter(value)
+                            retval.append(value)
+            ns_cache = self.cache.setdefault(namespace, {})
+            ns_cache[name] = retval
+            return retval
+        return get
+
+    def _getter_seq(namespace, name, converter):
+        def get(self):
+            cached = self.cache.get(namespace, {}).get(name)
+            if cached:
+                return cached
+            retval = []
+            for element in self.getElement("", namespace, name):
+                seqs = element.getElementsByTagNameNS(RDF_NAMESPACE, "Seq")
+                if len(seqs):
+                    for seq in seqs:
+                        for item in seq.getElementsByTagNameNS(RDF_NAMESPACE, "li"):
+                            value = self._getText(item)
+                            value = converter(value)
+                            retval.append(value)
+                else:
+                    value = converter(self._getText(element))
+                    retval.append(value)
+            ns_cache = self.cache.setdefault(namespace, {})
+            ns_cache[name] = retval
+            return retval
+        return get
+
+    def _getter_langalt(namespace, name, converter):
+        def get(self):
+            cached = self.cache.get(namespace, {}).get(name)
+            if cached:
+                return cached
+            retval = {}
+            for element in self.getElement("", namespace, name):
+                alts = element.getElementsByTagNameNS(RDF_NAMESPACE, "Alt")
+                if len(alts):
+                    for alt in alts:
+                        for item in alt.getElementsByTagNameNS(RDF_NAMESPACE, "li"):
+                            value = self._getText(item)
+                            value = converter(value)
+                            retval[item.getAttribute("xml:lang")] = value
+                else:
+                    retval["x-default"] = converter(self._getText(element))
+            ns_cache = self.cache.setdefault(namespace, {})
+            ns_cache[name] = retval
+            return retval
+        return get
+
+    def _getter_single(namespace, name, converter):
+        def get(self):
+            cached = self.cache.get(namespace, {}).get(name)
+            if cached:
+                return cached
+            value = None
+            for element in self.getElement("", namespace, name):
+                if element.nodeType == element.ATTRIBUTE_NODE:
+                    value = element.nodeValue
+                else:
+                    value = self._getText(element)
+                break
+            if value != None:
+                value = converter(value)
+            ns_cache = self.cache.setdefault(namespace, {})
+            ns_cache[name] = value
+            return value
+        return get
+
+    dc_contributor = property(_getter_bag(DC_NAMESPACE, "contributor", _converter_string))
+    """
+    Contributors to the resource (other than the authors). An unsorted
+    array of names.
+    """
+
+    dc_coverage = property(_getter_single(DC_NAMESPACE, "coverage", _converter_string))
+    """
+    Text describing the extent or scope of the resource.
+    """
+
+    dc_creator = property(_getter_seq(DC_NAMESPACE, "creator", _converter_string))
+    """
+    A sorted array of names of the authors of the resource, listed in order
+    of precedence.
+    """
+
+    dc_date = property(_getter_seq(DC_NAMESPACE, "date", _converter_date))
+    """
+    A sorted array of dates (datetime.datetime instances) of signifigance to
+    the resource.  The dates and times are in UTC.
+    """
+
+    dc_description = property(_getter_langalt(DC_NAMESPACE, "description", _converter_string))
+    """
+    A language-keyed dictionary of textual descriptions of the content of the
+    resource.
+    """
+
+    dc_format = property(_getter_single(DC_NAMESPACE, "format", _converter_string))
+    """
+    The mime-type of the resource.
+    """
+
+    dc_identifier = property(_getter_single(DC_NAMESPACE, "identifier", _converter_string))
+    """
+    Unique identifier of the resource.
+    """
+
+    dc_language = property(_getter_bag(DC_NAMESPACE, "language", _converter_string))
+    """
+    An unordered array specifying the languages used in the resource.
+    """
+
+    dc_publisher = property(_getter_bag(DC_NAMESPACE, "publisher", _converter_string))
+    """
+    An unordered array of publisher names.
+    """
+
+    dc_relation = property(_getter_bag(DC_NAMESPACE, "relation", _converter_string))
+    """
+    An unordered array of text descriptions of relationships to other
+    documents.
+    """
+
+    dc_rights = property(_getter_langalt(DC_NAMESPACE, "rights", _converter_string))
+    """
+    A language-keyed dictionary of textual descriptions of the rights the
+    user has to this resource.
+    """
+
+    dc_source = property(_getter_single(DC_NAMESPACE, "source", _converter_string))
+    """
+    Unique identifier of the work from which this resource was derived.
+    """
+
+    dc_subject = property(_getter_bag(DC_NAMESPACE, "subject", _converter_string))
+    """
+    An unordered array of descriptive phrases or keywrods that specify the
+    topic of the content of the resource.
+    """
+
+    dc_title = property(_getter_langalt(DC_NAMESPACE, "title", _converter_string))
+    """
+    A language-keyed dictionary of the title of the resource.
+    """
+
+    dc_type = property(_getter_bag(DC_NAMESPACE, "type", _converter_string))
+    """
+    An unordered array of textual descriptions of the document type.
+    """
+
+    pdf_keywords = property(_getter_single(PDF_NAMESPACE, "Keywords", _converter_string))
+    """
+    An unformatted text string representing document keywords.
+    """
+
+    pdf_pdfversion = property(_getter_single(PDF_NAMESPACE, "PDFVersion", _converter_string))
+    """
+    The PDF file version, for example 1.0, 1.3.
+    """
+
+    pdf_producer = property(_getter_single(PDF_NAMESPACE, "Producer", _converter_string))
+    """
+    The name of the tool that created the PDF document.
+    """
+
+    xmp_createDate = property(_getter_single(XMP_NAMESPACE, "CreateDate", _converter_date))
+    """
+    The date and time the resource was originally created.  The date and
+    time are returned as a UTC datetime.datetime object.
+    """
+
+    xmp_modifyDate = property(_getter_single(XMP_NAMESPACE, "ModifyDate", _converter_date))
+    """
+    The date and time the resource was last modified.  The date and time
+    are returned as a UTC datetime.datetime object.
+    """
+
+    xmp_metadataDate = property(_getter_single(XMP_NAMESPACE, "MetadataDate", _converter_date))
+    """
+    The date and time that any metadata for this resource was last
+    changed.  The date and time are returned as a UTC datetime.datetime
+    object.
+    """
+
+    xmp_creatorTool = property(_getter_single(XMP_NAMESPACE, "CreatorTool", _converter_string))
+    """
+    The name of the first known tool used to create the resource.
+    """
+
+    xmpmm_documentId = property(_getter_single(XMPMM_NAMESPACE, "DocumentID", _converter_string))
+    """
+    The common identifier for all versions and renditions of this resource.
+    """
+
+    xmpmm_instanceId = property(_getter_single(XMPMM_NAMESPACE, "InstanceID", _converter_string))
+    """
+    An identifier for a specific incarnation of a document, updated each
+    time a file is saved.
+    """
+
+    def custom_properties(self):
+        if not hasattr(self, "_custom_properties"):
+            self._custom_properties = {}
+            for node in self.getNodesInNamespace("", PDFX_NAMESPACE):
+                key = node.localName
+                while True:
+                    # see documentation about PDFX_NAMESPACE earlier in file
+                    idx = key.find(u_("\u2182"))
+                    if idx == -1:
+                        break
+                    key = key[:idx] + chr(int(key[idx+1:idx+5], base=16)) + key[idx+5:]
+                if node.nodeType == node.ATTRIBUTE_NODE:
+                    value = node.nodeValue
+                else:
+                    value = self._getText(node)
+                self._custom_properties[key] = value
+        return self._custom_properties
+
+    custom_properties = property(custom_properties)
+    """
+    Retrieves custom metadata properties defined in the undocumented pdfx
+    metadata schema.
+
+    :return: a dictionary of key/value items for custom metadata properties.
+    :rtype: dict
+    """