Example of a keystone object model

model.py

class BaseModel(object):
    def __init__(self, id=None):
        self.id = id or uuid.uuid4().hex

    @property
    def name(self):
        return self._name


class ProjectModel(BaseModel):
    def __init__(self, id=None, name):
        super(ProjectModel, self).__init__(id)
        self._name = name

    @property
    def name(self):
        return self._name

    @name.setter
    def name(self, value):
        self._name = value


class ValidatedProjectModel(ProjectModel):
    @name.setter
    def name(self, value):
        if not value:
            raise EmptyNameValueError(_('Name is required.'))
        if not isinstance(value, six.string):
            raise NameTypeMismatchValueError(_('Name must be a string.'))
        if len(value) > 64:
            raise NameTooLongValueError(_('Name is too long (must be less than 64 chars).'))
        if len(value) < 1:
            raise NameTooShortValueError(_('Name is too short (must be greater than 1 char).'))
        super(ValidatedProjectModel, self).name = value