code: def prepare(self, connection_id, sql, max_rows_total=None):
          
          request = requests_pb2.PrepareRequest()
          request.connection_id = connection_id
          request.sql = sql
          if max_rows_total is not None:
              request.max_rows_total = max_rows_total
  
          response_data = self._apply(request)
          response = responses_pb2.PrepareResponse()
          response.ParseFromString(response_data)
          return response.statement
docs: Prepares a statement.
  
          :param connection_id:
              ID of the current connection.
  
          :param sql:
              SQL query.
  
          :param max_rows_total:
              The maximum number of rows that will be allowed for this query.
  
          :returns:
              Signature of the prepared statement.