def __init__(self, **kwargs):
backend_cls = kwargs.pop("backend", None)
if backend_cls is None:
raise AttributeError("Missing 'backend' parameter.")
self.backend = import_class(backend_cls)(self)
schema = kwargs.pop("schema", None)
if schema is None:
raise AttributeError("Missing 'schema' parameter.")
elif isinstance(schema, dict):
self.schema = DBSchema.from_dict(schema)
elif isinstance(schema, str):
self.schema = DBSchema.from_json(schema)
self.options = kwargs
