code: def _pop_letters(char_list):
      
      logger.debug('_pop_letters(%s)', char_list)
      letters = []
      while len(char_list) != 0 and char_list[0].isalpha():
          letters.append(char_list.pop(0))
      logger.debug('got letters: %s', letters)
      logger.debug('updated char list: %s', char_list)
      return letters
docs: Pop consecutive letters from the front of a list and return them
  
      Pops any and all consecutive letters from the start of the provided
      character list and returns them as a list of characters. Operates
      on (and possibly alters) the passed list
  
      :param list char_list: a list of characters
      :return: a list of characters
      :rtype: list