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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def getDatastream(self, pid, dsID, asOfDateTime=None, validateChecksum=False):
 """Get information about a single datastream on a Fedora object; optionally, get information for the version of the datastream as of a particular date time. :param pid: object pid :param dsID: datastream id :param asOfDateTime: optional datetime; ``must`` be a non-naive datetime so it can be converted to a date-time format Fedora can understand :param validateChecksum: boolean; if True, request Fedora to recalculate and verify the stored checksum against actual data :rtype: :class:`requests.models.Response` """

        # /objects/{pid}/datastreams/{dsID} ? [asOfDateTime] [format] [validateChecksum]
        http_args = {}
        if validateChecksum:
            # fedora only responds to lower-case validateChecksum option
            http_args['validateChecksum'] = str(validateChecksum).lower()
        if asOfDateTime:
            http_args['asOfDateTime'] = datetime_to_fedoratime(asOfDateTime)
        http_args.update(self.format_xml)
        uri = 'objects/%(pid)s/datastreams/%(dsid)s' % {'pid': pid, 'dsid': dsID}
        return self.get(uri, params=http_args)