Set the euler angles
        :param euler: list or array of the euler angles [roll, pitch, yaw]

def euler(self, euler):
        """
        Set the euler angles
        :param euler: list or array of the euler angles [roll, pitch, yaw]

        """
        assert(len(euler) == 3)
        self._euler = np.array(euler)

        # mark other representations as outdated, will get generated on next
        # read
        self._q = None
        self._dcm = None