def callKeyedMethod(obj, key, *args, **kwargs):
  """
  Resolves a keyed method by the given key and and calls it with the given
  arguments.
  """
  return iKeyedMethods(type(obj))[key].__get__(obj)(*args, **kwargs)

def iKeyedMethods(aClass):
  """
  Returns a dict of all KeyedMethods of the given class indexed by key. The dict
  contains the KeyedMethods of all super classes that are not hidden by the
  method resolution order.
  """
  if not '_iKeyedMethods' in vars(aClass):
    methods = {}
    for _name, attr in mKeyedMethods(aClass).items():
      if attr.key in methods:
        raise ValueError()
      methods[attr.key] = attr
    aClass._iKeyedMethods = methods
  return aClass._iKeyedMethods

def keyedMethod(key):
  """
  Can be used to decorate a method with a key
  """
  return lambda fget: KeyedMethod(key, fget)

def lKeyedMethods(aClass):
  """
  Returns a dict of all KeyedMethods of the given class indexed by attribute
  name. The dict does not contain the KeyedMethods of any super class.
  """
  if aClass is object:
    return {}

  lAttrs = vars(aClass)
  if not '_lKeyedMethods' in lAttrs:
    methods = {}
    for name, attr in lAttrs.items():
      if isinstance(attr, KeyedMethod):
        methods[name] = attr
    aClass._lKeyedMethods = methods
  return aClass._lKeyedMethods

def mKeyedMethods(aClass):
  """
  Returns a dict of all KeyedMethods of the given class indexed by attribute
  name. The dict contains the KeyedMethods of all super classes that are not
  hidden by the method resolution order.
  """
  if not '_mKeyedMethods' in vars(aClass):
    methods = {}
    for sClass in reversed(aClass.mro()):
      methods.update(lKeyedMethods(sClass))
    aClass._mKeyedMethods = methods
  return aClass._mKeyedMethods

class KeyedMethod():

  def __init__(self, key, fget):
    self.__key = key
    self.__fget = fget
    self.__doc__ = fget.__doc__

  @property
  def key(self):
    return self.__key

  @property
  def fget(self):
    return self.__fget

  def __get__(self, obj, objType=None):
    if obj is None:
      return self
    if self.__fget is None:
      raise AttributeError("unreadable attribute")
    return lambda *args, **kwargs: self.__fget(obj, *args, **kwargs)