Ch1 TFP: Specify the posterior sampler

[Bazman76]

Hi there,

This section:

], kernel_results = graph_sample_chain(
    num_results=num_results,
    num_burnin_steps=num_burnin_steps,
    current_state=initial_chain_state,
    kernel = kernel)

Is giving the following error:

TypeError: Tensor is unhashable. Instead, use tensor.ref() as the key.