code: def parse_block_scalar_empty_line(IndentTokenClass, ContentTokenClass):
      
      def callback(lexer, match, context):
          text = match.group()
          if (context.block_scalar_indent is None or
                  len(text) <= context.block_scalar_indent):
              if text:
                  yield match.start(), IndentTokenClass, text
          else:
              indentation = text[:context.block_scalar_indent]
              content = text[context.block_scalar_indent:]
              yield match.start(), IndentTokenClass, indentation
              yield (match.start()+context.block_scalar_indent,
                      ContentTokenClass, content)
          context.pos = match.end()
      return callback
docs: Process an empty line in a block scalar.