docs: def is_timestamp_valid(self, timestamp):
          """Timestamp must be string in %Y-%m-%dT%H:%M:%S. format """
  
          try:
              timestamp_server = datetime.utcnow()
              timestamp_client = datetime.strptime(timestamp, "%Y-%m-%dT%H:%M:%S")
  
              d1_ts = time.mktime(timestamp_client.timetuple())
              d2_ts = time.mktime(timestamp_server.timetuple())
  
              diff = int(d2_ts-d1_ts) / 60
  
              if diff > self.timestamp_window:
                  raise ImmediateHttpResponse(response=HttpBadRequest('Exceeded timestamp window'))
          except Exception, e:
              raise ImmediateHttpResponse(response=HttpBadRequest('Unknown error on timestamp validation'))
  
          return True