code: def filter(stream_spec, filter_name, *args, **kwargs):
      
      return filter_multi_output(stream_spec, filter_name, *args, **kwargs).stream()
docs: Apply custom filter.
  
      ``filter_`` is normally used by higher-level filter functions such as ``hflip``, but if a filter implementation
      is missing from ``fmpeg-python``, you can call ``filter_`` directly to have ``fmpeg-python`` pass the filter name
      and arguments to ffmpeg verbatim.
  
      Args:
          stream_spec: a Stream, list of Streams, or label-to-Stream dictionary mapping
          filter_name: ffmpeg filter name, e.g. `colorchannelmixer`
          *args: list of args to pass to ffmpeg verbatim
          **kwargs: list of keyword-args to pass to ffmpeg verbatim
  
      The function name is suffixed with ``_`` in order avoid confusion with the standard python ``filter`` function.
  
      Example:
  
          ``ffmpeg.input('in.mp4').filter('hflip').output('out.mp4').run()``