Gets the first row of the data table, with serialize_cell or self.get_cell_value is called on
    each cell.

def headers(self, serialize_cell=None):
    """Gets the first row of the data table, with serialize_cell or self.get_cell_value is called on
    each cell."""
    if serialize_cell is None:
      serialize_cell = self.get_cell_value
    return [serialize_cell(cell) for cell in self.rows[0]]