code: def operator(name=None, operators=None, aliases=None, kind=None):
      
      def delegator(assertion, subject, expected, *args, **kw):
          return assertion.test(subject, expected, *args, **kw)
  
      def decorator(fn):
          operator = Operator(fn=fn, aliases=aliases, kind=kind)
          _name = name if isinstance(name, six.string_types) else fn.__name__
          operator.operators = (_name,)
  
          _operators = operators
          if isinstance(_operators, list):
              _operators = tuple(_operators)
  
          if isinstance(_operators, tuple):
              operator.operators += _operators
  
          # Register operator
          Engine.register(operator)
          return functools.partial(delegator, operator)
  
      return decorator(name) if inspect.isfunction(name) else decorator
docs: Registers a new operator function in the test engine.
  
      Arguments:
          *args: variadic arguments.
          **kw: variadic keyword arguments.
  
      Returns:
          function