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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 GetFileSystemReferenceCount(self, path_spec):
 """Retrieves the reference count of a cached file system object. Args: path_spec (PathSpec):
 path specification. Returns: int: reference count or None if there is no file system object for the corresponding path specification cached. """

    identifier = self._GetFileSystemCacheIdentifier(path_spec)
    cache_value = self._file_system_cache.GetCacheValue(identifier)
    if not cache_value:
      return None

    return cache_value.reference_count