docs: def get_cas(key_options, global_options, item):
      """
      Get the CAS from various inputs. This will properly honor
      the ``ignore_cas`` flag, if present.
  
      :param key_options: Key specific options
      :param global_options: Global options
      :param item: The item
      :return: The cas, or 0 if no cas
      """
      if item:
          ign_cas = get_option('ignore_cas', key_options, globals(), False)
          return 0 if ign_cas else item.cas
      else:
          try:
              cas = key_options['cas']
          except KeyError:
              try:
                  cas = global_options['cas']
              except KeyError:
                  return 0
          if not cas:
              return 0
          return cas