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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 GetExpirationTime(self):
 """Computes the timestamp at which this breakpoint will expire."""

    # TODO(emrekultursay): Move this to a common method.
    if '.' not in self.definition['createTime']:
      fmt = '%Y-%m-%dT%H:%M:%S%Z'
    else:
      fmt = '%Y-%m-%dT%H:%M:%S.%f%Z'

    create_datetime = datetime.strptime(
        self.definition['createTime'].replace('Z', 'UTC'), fmt)
    return create_datetime + self.expiration_period