def get_column_header_for_number(self, column_var_names, header=False):
        """This function subtracts 1 from inputted column number to comply
        with programmers counting (i.e. from 0, not from 1). For TSV data."""
        if not header:
            header = self.oldheader
        for col in column_var_names:
            value = getattr(self, col)
            if not value or value is None:
                continue
            setattr(self, col, self.number_to_headerfield(value, header))