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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _J(self, theta):
 """ Implements the order dependent family of functions defined in equations 4 to 7 in the reference paper. """

        if self.order == 0:
            return np.pi - theta
        elif self.order == 1:
            return tf.sin(theta) + (np.pi - theta) * tf.cos(theta)
        elif self.order == 2:
            return 3. * tf.sin(theta) * tf.cos(theta) + \
                   (np.pi - theta) * (1. + 2. * tf.cos(theta) ** 2)