docs: 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)