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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 _generate_storage_broker_lookup():
 """Return dictionary of available storage brokers."""

    storage_broker_lookup = dict()
    for entrypoint in iter_entry_points("dtool.storage_brokers"):
        StorageBroker = entrypoint.load()
        storage_broker_lookup[StorageBroker.key] = StorageBroker
    return storage_broker_lookup