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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(cls, context_id, persistence_engine=None):
 """Load and instantiate a Context from the persistence_engine."""

        if not persistence_engine:
            from furious.config import get_default_persistence_engine
            persistence_engine = get_default_persistence_engine()

        if not persistence_engine:
            raise RuntimeError(
                'Specify a valid persistence_engine to load the context.')

        return persistence_engine.load_context(context_id)