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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 list_ctx(self):
 """Returns a list of contexts this parameter is initialized on."""

        if self._data is None:
            if self._deferred_init:
                return self._deferred_init[1]
            raise RuntimeError("Parameter '%s' has not been initialized"%self.name)
        return self._ctx_list