'Sets the (flattened, log-transformed) non-fixed hyperparameters.
Parameters
theta : array, shape (n_dims,)
The non-fixed, log-transformed hyperparameters of the kernel'

@theta.setter
def theta(self, theta):

    k1_dims = self.k1.n_dims
    self.k1.theta = theta[:k1_dims]
    self.k2.theta = theta[k1_dims:]
