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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def register(self, key_or_value=None):
 """Decorator to register a function, or registration itself. This is primarily intended for use as a decorator, either with or without a key/parentheses. ```python @my_registry.register('key1') def value_fn(x, y, z):
 pass @my_registry.register() def another_fn(x, y):
 pass @my_registry.register def third_func():
 pass ``` Note if key_or_value is provided as a non-callable, registration only occurs once the returned callback is called with a callable as its only argument. ```python callback = my_registry.register('different_key') 'different_key' in my_registry # False callback(lambda (x, y):
 x + y) 'different_key' in my_registry # True ``` Args: key_or_value (optional):
 key to access the registered value with, or the function itself. If `None` (default), `self.default_key` will be called on `value` once the returned callback is called with `value` as the only arg. If `key_or_value` is itself callable, it is assumed to be the value and the key is given by `self.default_key(key)`. Returns: decorated callback, or callback generated a decorated function. """


    def decorator(value, key):
      self[key] = value
      return value

    # Handle if decorator was used without parens
    if callable(key_or_value):
      return decorator(value=key_or_value, key=None)
    else:
      return lambda value: decorator(value, key=key_or_value)