'Returns the log-transformed bounds on the theta.
Returns
bounds : array, shape (n_dims, 2)
The log-transformed bounds on the kernel\'s hyperparameters theta'

@property
def bounds(self):

    bounds = []
    for hyperparameter in self.hyperparameters:
        if (not hyperparameter.fixed):
            bounds.append(hyperparameter.bounds)
    if (len(bounds) > 0):
        return np.log(np.vstack(bounds))
    else:
        return np.array([])
