docs: def convert_audio(self, file_path, new_mimetype, overwrite=False):
  
          '''
              a method to convert an audio file into a different codec
              
          :param file_path: string with path to file on localhost 
          :param new_mimetype: string with mimetype for new file
          :param overwrite: [optional] boolean to overwrite existing file
          :return: string with path to new file on localhost
          
              SEE: https://github.com/Ch00k/ffmpy
          '''
  
          title = '%s.convert_audio' % self.__class__.__name__
  
      # validate inputs
          input_fields = {
              'file_path': file_path,
              'new_mimetype': new_mimetype
          }
          for key, value in input_fields.items():
              object_title = '%s(%s=%s)' % (title, key, str(value))
              self.fields.validate(value, '.%s' % key, object_title)
  
      # retrieve file extension
          new_extension = ''
          mimetype_list = []
          mime_arg = '%s(new_mimetype=%s)' % (title, new_mimetype)
          for key, value in self.fields.schema['audio_extensions'].items():
              mimetype_list.append(value['mimetype'])
              if value['mimetype'] == new_mimetype:
                  new_extension = value['extension']
                  break
          if not new_extension:
              raise ValueError('%s must be one of %s mimetypes' % (mime_arg, mimetype_list))
  
      # import dependencies
          from os import path
          import ffmpy
  
      # validate existence of file
          file_arg = '%s(file_path=%s)' % (title, file_path)
          if not path.exists(file_path):
              raise ValueError('%s is not a valid path', file_arg)
  
      # construct new file
          file_name, file_extension = path.splitext(file_path)
          output_path = file_name + new_extension
  
      # construct inputs
          ffmpeg_kwargs = {
              'inputs': {file_path: None},
              'outputs': {output_path: None},
              'global_options': [ '-v error']
          }
          if overwrite:
              ffmpeg_kwargs['global_options'].append('-y')
          ffmpeg_client = ffmpy.FFmpeg(**ffmpeg_kwargs)
  
      # run conversion
          ffmpeg_client.run()
  
          return output_path