code: def _find_column_label_positions(self, match_value_or_fct, levels=None):
          
          allmatches = find_locations(self.df.columns, match_value_or_fct, levels)
          if allmatches and self.inc_index:  # tramslate back
              allmatches = [m + self.nidxs for m in allmatches]
          return allmatches
docs: Check the original DataFrame's column labels to find the locations of columns. And return the adjusted
          column indexing within region (offset if including index)