docs: def indentation(logical_line, previous_logical, indent_char,
                  indent_level, previous_indent_level):
      """
      Use 4 spaces per indentation level.
  
      For really old code that you don't want to mess up, you can continue to
      use 8-space tabs.
      """
      if indent_char == ' ' and indent_level % 4:
          return 0, "E111 indentation is not a multiple of four"
      indent_expect = previous_logical.endswith(':')
      if indent_expect and indent_level <= previous_indent_level:
          return 0, "E112 expected an indented block"
      if indent_level > previous_indent_level and not indent_expect:
          return 0, "E113 unexpected indentation"