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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 atlas_node_add_callback(atlas_state, callback_name, callback):
 """ Add a callback to the initialized atlas state """

    if callback_name == 'store_zonefile':
        atlas_state['zonefile_crawler'].set_store_zonefile_callback(callback)

    else:
        raise ValueError("Unrecognized callback {}".format(callback_name))