code: def execute(self, sources, target):
          
          existing_ml_fields = self._get_fields_list_from_eps(sources)
          dup_ml_fields = [f.copy() for f in self.fields]
          if self.is_append:
              src = list([copy.deepcopy(f) for f in existing_ml_fields[0]])
              src.extend(dup_ml_fields)
              target._ml_fields = src
          else:
              target._ml_fields = self.fields
docs: :type sources: list[DFAdapter]
          :type target: DFAdapter