in doubles/proxy.py [0:0]
def method_double_for(self, method_name):
"""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
"""
if method_name not in self._method_doubles:
self._method_doubles[method_name] = MethodDouble(method_name, self._target)
return self._method_doubles[method_name]