docs: def generate_from_directory(cls, directory):
          """Create a parser by defining which input files it will read from.
  
          Input:
              directory - str, directory to read from
              files - str, list of files from which to search.
              """
          files = [os.path.join(directory, f) for f in os.listdir(directory)
                   if os.path.isfile(os.path.join(directory, f))]
          return cls(files)