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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 GetCacheValueByObject(self, vfs_object):
 """Retrieves the cache value for the cached object. Args: vfs_object (object):
 VFS object that was cached. Returns: tuple[str, ObjectsCacheValue]: identifier and cache value object or (None, None) if not cached. Raises: RuntimeError: if the cache value is missing. """

    for identifier, cache_value in iter(self._values.items()):
      if not cache_value:
        raise RuntimeError('Missing cache value.')

      if cache_value.vfs_object == vfs_object:
        return identifier, cache_value

    return None, None