docs: def SplitMeta(meta):
      """Split and validate metacharacters.
  
    Example: '{}' -> ('{', '}')
  
    This is public so the syntax highlighter and other tools can use it.
    """
      n = len(meta)
      if n % 2 == 1:
          raise ConfigurationError(
              '%r has an odd number of metacharacters' % meta)
      return meta[:n // 2], meta[n // 2:]