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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _add_column(self, label, field):
 """ Add a new column to the table. It will have the header text ``label``, but for data inserts and queries, the ``field`` name must be used. If necessary, this will expand the size of the sheet itself to allow for the new column. """

        # Don't call this directly.
        assert self.headers is not None
        cols = 0
        if len(self._headers) > 0:
            cols = max([int(c.cell.col) for c in self._headers])
        new_col = cols + 1
        if int(self._ws.col_count.text) < new_col:
            self._ws.col_count.text = str(new_col)
            self._update_metadata()

        cell = self._service.UpdateCell(1, new_col, label,
                                        self._ss.id, self.id)
        self._headers.append(cell)