tf.matrix_band_part(input, num_lower, num_upper, name=None)
Copy a tensor setting everything outside a central band in each innermost matrix
to zero.
The band part is computed as follows: Assume input has k dimensions [I, J, K, ..., M, N], then the output is a tensor with the same shape where
band[i, j, k, ..., m, n] = in_band(m, n) * input[i, j, k, ..., m, n].
The indicator function 'in_band(m, n)is one if(num_lower < 0 || (m-n) <= num_lower)) && (num_upper < 0 || (n-m) <=