Add a Role to the project and returns a :class:`Role` object.

        :param name: name of the :class:`Role`
        :param attrs: optional attributes for :class:`Role`

def add_role(self, name, **attrs):
        """
        Add a Role to the project and returns a :class:`Role` object.

        :param name: name of the :class:`Role`
        :param attrs: optional attributes for :class:`Role`
        """
        return Roles(self.requester).create(self.id, name, **attrs)