docs: def list_files(x, path=""):
      """
      Lists file(s) in given path of the X type.
      :param str x: File extension that we are interested in.
      :param str path: Path, if user would like to check a specific directory outside of the CWD
      :return list of str: File name(s) to be worked on
      """
      logger_directory.info("enter list_files")
      file_list = []
      if path:
          # list files from target directory
          files = os.listdir(path)
          for file in files:
              if file.endswith(x) and not file.startswith(("$", "~", ".")):
                  # join the path and basename to create full path
                  file_list.append(os.path.join(path, file))
      else:
          # list files from current working directory
          files = os.listdir()
          for file in files:
              if file.endswith(x) and not file.startswith(("$", "~", ".")):
                  # append basename. not full path
                  file_list.append(file)
      logger_directory.info("exit list_files")
      return file_list