code: def _indent(text, prefix, predicate=None):
      
      if predicate is None:
          predicate = lambda line: line.strip()
  
      def prefixed_lines():
          for line in text.splitlines(True):
              yield prefix + line if predicate(line) else line
  
      return "".join(prefixed_lines())
docs: Adds 'prefix' to the beginning of selected lines in 'text'.
  
      If 'predicate' is provided, 'prefix' will only be added to the lines
      where 'predicate(line)' is True. If 'predicate' is not provided,
      it will default to adding 'prefix' to all non-empty lines that do not
      consist solely of whitespace characters.