code: def parse_block_scalar_empty_line(indent_token_class, content_token_class):
          
          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(), indent_token_class, text
              else:
                  indentation = text[:context.block_scalar_indent]
                  content = text[context.block_scalar_indent:]
                  yield match.start(), indent_token_class, indentation
                  yield (match.start()+context.block_scalar_indent,
                         content_token_class, content)
              context.pos = match.end()
          return callback
docs: Process an empty line in a block scalar.