code: def method_double_for(self, method_name):
          
  
          if method_name not in self._method_doubles:
              self._method_doubles[method_name] = MethodDouble(method_name, self._target)
  
          return self._method_doubles[method_name]
docs: Returns the method double for the provided method name, creating one if necessary.
  
          :param str method_name: The name of the method to retrieve a method double for.
          :return: The mapped ``MethodDouble``.
          :rtype: MethodDouble