code: def build_operator(self):
      return tf.linalg.LinearOperatorBlockLowerTriangular(
          [
              [
                  tf.linalg.LinearOperatorDiag(
                      diag=[2.0, 3.0, 6.0], is_non_singular=True
                  )
              ],
              [
                  tf.linalg.LinearOperatorFullMatrix(
                      matrix=[[12.0, 5.0, -1.0], [3.0, 0.0, 1.0]]
                  ),
                  tf.linalg.LinearOperatorIdentity(2),
              ],
          ],
          is_non_singular=True,
      )
  
imports: import numpy
  import tensorflow.compat.v2
  from tensorflow_probability.python.bijectors import scale_matvec_linear_operator
  from tensorflow_probability.python.internal import test_util
label_desc: Use image node_id 1 for calling the ScaleMatvecLinearOperatorBlockTrilTest obj's underlying member method code with example usage: obj.build_operator() and returns: tf