          return retval
  
      @classmethod
      def _validate_inputs(cls,
                           filter_files: Optional[Union[str, List[str]]],
                           nfilter_files: Optional[Union[str, List[str]]]) -> Tuple[List[str],
                                                                                    List[str]]:
          """ Validates that the given filter/nfilter files exist, are image files and are unique
  
          Parameters
          ----------
          filter_files: str, list or ``None``
 
</s> remove         filter_files: str, list or ``None``
 </s> add         filter_files: list or ``None`` </s> remove                  filter_files: Optional[Union[str, List[str]]],
                 nfilter_files: Optional[Union[str, List[str]]],
 </s> add                  filter_files: Optional[List[str]],
                 nfilter_files: Optional[List[str]], </s> remove         nfilter_files: str, list or ``None``
 </s> add         nfilter_files: list or ``None`` </s> remove     nfilter_files: str, list or ``None``
 </s> add     nfilter_files: list or ``None`` </s> remove     filter_files: str, list or ``None``
 </s> add     filter_files: list or ``None``
                         filter_files: Optional[List[str]],
                         nfilter_files: Optional[List[str]]) -> Tuple[List[str], List[str]]:
          return retval
  
      @classmethod
      def _validate_inputs(cls,
                         filter_files: Optional[List[str]],
                         nfilter_files: Optional[List[str]]) -> Tuple[List[str], List[str]]:
                         filter_files: Optional[List[str]],
                         nfilter_files: Optional[List[str]]) -> Tuple[List[str], List[str]]:
                         filter_files: Optional[List[str]],
                         nfilter_files: Optional[List[str]]) -> Tuple[List[str], List[str]]:
          """ Validates that the given filter/nfilter files exist, are image files and are unique
  
          Parameters
          ----------
          filter_files: str, list or ``None``
keep keep keep keep replace replace replace keep keep keep keep keep
 Face-filter updates:
  - Allow selecting folder as well as multiple images
  - Lower default threshold and update helptext
  - bugfix: detector error when using all aligned faces
  - Standardize output folder name 
scripts/extract.py