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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 restoreState(self):
 """Utility method to restore plugin state from persistent storage to permit access to previous plugin state. @return: Object that stores plugin state. """

        if os.path.exists(self._stateFile):
            try:
                fp = open(self._stateFile,  'r')
                stateObj = pickle.load(fp)
            except:
                raise IOError("Failure in reading plugin state from file: %s" 
                              % self._stateFile)
            return stateObj
        return None