code: def _init_db(cls):
          
          # This list of import defines which SQLAlchemy classes will be
          # initialized when Meta.init() is called. If a sqlalchemy class is not
          # imported before the call to create_all(), it will not be created.
          import fonduer.candidates.models  # noqa
          import fonduer.features.models  # noqa
          import fonduer.learning.models  # noqa
          import fonduer.parser.models  # noqa
          import fonduer.supervision.models  # noqa
          import fonduer.utils.models  # noqa
  
          logger.info("Initializing the storage schema")
          Meta.Base.metadata.create_all(Meta.engine)
docs: Initialize the storage schema.
  
          This call must be performed after all classes that extend
          Base are declared to ensure the storage schema is initialized.