code: def eof():
      '''Parser EOF flag of a string.'''
      @Parser
      def eof_parser(text, index=0):
          if index >= len(text):
              return Value.success(index, None)
          else:
              return Value.failure(index, 'EOF')
      return eof_parsef eof():
      '''Parser EOF flag of a string.'''
      @Parser
      def eof_parser(text, index=0):
          if index >= len(text):
              return Value.success(index, None)
          else:
              return Value.failure(index, 'EOF')
      return eof_parser
docs: Parser EOF flag of a string.