text: # -*- coding: utf-8 -*-
  #
  # Copyright 2017 Ricequant, Inc
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  import inspect
  
  
  class CachedProperty(object):
  
      def __init__(self, func):
          self.func = func
  
      def __get__(self, obj, cls):
          if obj is None:
              return self
          if "__cached__" not in obj.__dict__:
              obj.__dict__["__cached__"] = []
          value = obj.__dict__[self.func.__name__] = self.func(obj)
          obj.__dict__["__cached__"].append(self.func.__name__)
          return value
  
      @property
      def annotation(self):
          return inspect.signature(self.func).return_annotation
  
  
  def clear_cache(obj):
      if "__cached__" not in obj.__dict__:
          return
      for cached_key in obj.__dict__["__cached__"]:
          obj.__dict__.pop(cached_key)
      obj.__dict__["__cached__"] = []