code: def _get_column_widths(self):
          
          col_widths = {}
          for table, (row, col) in self.__tables.values():
              for colname, width in table.column_widths.items():
                  ic = col + table.get_column_offset(colname)
                  current_width = col_widths.setdefault(ic, width)
                  col_widths[ic] = max(width, current_width)
          return col_widths
docs: return a dictionary of {col -> width}