code: def GetNumberOfRows(self, table_name):
      
      if not self._connection:
        raise IOError('Not opened.')
  
      self._cursor.execute(self._NUMBER_OF_ROWS_QUERY.format(table_name))
      row = self._cursor.fetchone()
      if not row:
        raise IOError(
            'Unable to retrieve number of rows of table: {0:s}'.format(
                table_name))
  
      number_of_rows = row[0]
      if isinstance(number_of_rows, py2to3.STRING_TYPES):
        try:
          number_of_rows = int(number_of_rows, 10)
        except ValueError as exception:
          raise IOError((
              'Unable to determine number of rows of table: {0:s} '
              'with error: {1!s}').format(table_name, exception))
  
      return number_of_rows
docs: Retrieves the number of rows in the table.
  
      Args:
        table_name (str): name of the table.
  
      Returns:
        int: number of rows.
  
      Raises:
        IOError: if the file-like object has not been opened.
        OSError: if the file-like object has not been opened.