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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 get_timestamp(self, **kwargs):
 """Retrieves the timestamp for a given set of data"""

        timestamp = kwargs.get('timestamp')
        if not timestamp:
            now = datetime.datetime.utcnow()
            timestamp = now.strftime("%Y-%m-%dT%H:%M:%S") + ".%03d" % (now.microsecond / 1000) + "Z"

        return timestamp