def execute(self, sources, target):
        """
        :type sources: list[DFAdapter]
        :type target: DFAdapter
        """
        fields = self._get_fields_list_from_eps(sources)
        ret_fields = fields[0]
        if self.clear_feature:
            ret_fields = list(self._remove_field_roles(ret_fields, set(six.iterkeys(self.field_mapping)),
                                                       FieldRole.FEATURE))
        target._ml_fields = list(self._set_singleton_role(ret_fields, self.field_mapping))
:type sources: list[DFAdapter]
        :type target: DFAdapter