class_docstr: Most tests done in the base class LinearOperatorDerivedClassTest.
class_docstr_tok: ["Most","tests","done","in","the","base","class","LinearOperatorDerivedClassTest","."]
code: def operator_and_matrix(
      self,
      build_info,
      dtype,
      use_placeholder,
      ensure_self_adjoint_and_pd=False,
  ):
      shape = list(build_info.shape)
      # Upper triangle will be nonzero, but ignored.
      # Use a diagonal that ensures this matrix is well conditioned.
      tril = linear_operator_test_util.random_tril_matrix(
          shape,
          dtype=dtype,
          force_well_conditioned=True,
          remove_upper=False,
      )
      if ensure_self_adjoint_and_pd:
          # Get the diagonal and make the matrix out of it.
          tril = array_ops.matrix_diag_part(tril)
          tril = math_ops.abs(tril) + 1e-1
          tril = array_ops.matrix_diag(tril)
  
      lin_op_tril = tril
  
      if use_placeholder:
          lin_op_tril = array_ops.placeholder_with_default(
              lin_op_tril, shape=None
          )
  
      operator = linalg.LinearOperatorLowerTriangular(
          lin_op_tril,
          is_self_adjoint=True if ensure_self_adjoint_and_pd else None,
          is_positive_definite=True
          if ensure_self_adjoint_and_pd
          else None,
      )
  
      matrix = array_ops.matrix_band_part(tril, -1, 0)
  
      return operator, matrix
  
imports: from tensorflow.python.framework import config
  from tensorflow.python.framework import test_util
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import math_ops
  from tensorflow.python.ops import variables
  from tensorflow.python.ops.linalg import linalg
  from tensorflow.python.ops.linalg import linear_operator_test_util
  from tensorflow.python.platform import test
label_desc: Use image node_id 2 for calling the LinearOperatorLowerTriangularTest obj's underlying member method code with example usage: obj.operator_and_matrix(build_info, dtype, use_placeholder, ensure__adjoint_and_pd) and returns: operator,  matrix