def _attach_fields(obj):
for attr in base_fields.__all__:<EOL><INDENT>if not hasattr(obj, attr):<EOL><INDENT>setattr(obj, attr, getattr(base_fields, attr))<EOL><DEDENT><DEDENT>for attr in fields.__all__:<EOL><INDENT>setattr(obj, attr, getattr(fields, attr))<EOL><DEDENT>
Attach all the marshmallow fields classes to ``obj``, including
    Flask-Marshmallow's custom fields.