def tf_kl_divergence(self, distr_params1, distr_params2):
raise NotImplementedError<EOL>
Creates the tensorFlow operations for calculating the KL divergence between two  
distributions.

Args:
    distr_params1: tuple of parameter tensors for first distribution.
    distr_params2: tuple of parameter tensors for second distribution.

Returns:
    KL divergence tensor.