code: def set_block_scalar_indent(token_class):
          
          def callback(lexer, match, context):
              text = match.group()
              context.block_scalar_indent = None
              if not text:
                  return
              increment = match.group(1)
              if increment:
                  current_indent = max(context.indent, 0)
                  increment = int(increment)
                  context.block_scalar_indent = current_indent + increment
              if text:
                  yield match.start(), token_class, text
                  context.pos = match.end()
          return callback
docs: Set an explicit indentation level for a block scalar.