Computes mask on sub-episodes which includes only contiguous components.

next_time_steps_discount Tensor of shape [batch_size, total_steps] corresponding to environment discounts on next time steps (i.e.

A float Tensor of shape [batch_size, total_steps] specifying mask including only contiguous components. Each row will be of the form [1.0] * a + [0.0] * b, where a >= 1 and b >= 0, and in which the initial sequence of ones corresponds to a contiguous sub-episode.