Driver function to fetch the data from the two collections

def get_collections_data(self):
        """
            Driver function to fetch the data from the two collections
        """

        collections = {
            'left': self.left_collection,
            'right': self.right_collection
        }
        for collection_type, collection in collections.iteritems():
            pipeline = self.build_pipeline(collection)
            self.collections_data[collection_type] = self.fetch_and_process_data(
                collection, pipeline)