code: def _default_output_prefix(filenames):
      
  
      if isinstance(filenames, (str, )):
          filenames = [filenames]
      common_prefix, ext = os.path.splitext(os.path.commonprefix(
          map(os.path.basename, filenames)))
      common_prefix = common_prefix.rstrip("_-")
      return common_prefix if len(common_prefix) > 0 else "sick"
docs: Return a default filename prefix for output files based on the input files.
  
      :param filenames:
          The input filename(s):
  
      :type filenames:
          str or list of str
  
      :returns:
          The extensionless common prefix of the input filenames:
  
      :rtype:
          str