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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 _load_from_cache_if_available(self, key):
 """Returns a cached Model instance given the entity key if available. Args: key: Key instance. Returns: A Model instance if the key exists in the cache. """

    if key in self._cache:
      entity = self._cache[key]  # May be None, meaning "doesn't exist".
      if entity is None or entity._key == key:
        # If entity's key didn't change later, it is ok.
        # See issue 13.  http://goo.gl/jxjOP
        raise tasklets.Return(entity)