code: def _pop_a_match_at_tier(op1, operator_list, tier):
      # Search from the back of list to the front in order to create nice default
      # order of operations.
      for i in range(1, len(operator_list) + 1):
          op2 = operator_list[-i]
          for adder in tier:
              if adder.can_add(op1, op2):
                  return operator_list.pop(-i), adder
      return None, None
  
imports: import abc
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import tensor_shape
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import check_ops
  from tensorflow.python.ops.linalg import linear_operator
  from tensorflow.python.ops.linalg import linear_operator_diag
  from tensorflow.python.ops.linalg import linear_operator_full_matrix
  from tensorflow.python.ops.linalg import linear_operator_identity
  from tensorflow.python.ops.linalg import linear_operator_lower_triangular
label_desc: Use image node_id 2 for calling a global function with example usage: _pop_a_match_at_tier(op1, operator_list, tier) and returns: None,  None, operator_list,  adder