std::vector<absl::string_view> equation_split =
      absl::StrSplit(equation, "->");
  if (equation_split.size() != 2) {
    return errors::InvalidArgument("Equation must contain a single ->");
  }

  const absl::string_view input_subs = equation_split[0];
  const absl::string_view output_subs = equation_split[1];
  if (op.num_inputs() == 1) {