@classmethod
    def definition(cls, **kwargs):
        schema = super(GroupField, cls).definition(**kwargs)
        # Keep the ``type`` node only
        schema.children = [c for c in schema.children
                           if ('hint', 'name', 'required') not in c.name]
        schema.add(SchemaNode(String(), name='description', missing=drop))
        schema.add(SchemaNode(Sequence(), SchemaNode(TypeFieldNode()),
                              name='fields', validator=Length(min=1)))
        return schema
dataset/ETHPy150Open spiral-project/daybed/daybed/schemas/base.py/GroupField.definition/swapped operands of `not in`