code: def _execute(self, connection, query, fetch=True):
          
          # execute query
          with connection.cursor() as cursor:
              cursor.execute(query)
              if fetch:
                  return cursor.fetchall()
              else:
                  cursor.execute('COMMIT;')
docs: Executes given query and returns result.
  
          Args:
              connection: connection to postgres database who stores mpr data.
              query (str): sql query
              fetch (boolean, optional): if True, fetch query result and return it. If False, do not fetch.
  
          Returns:
              iterable with query result or None if fetch is False.