docs: public SDVariable[] getInputVariablesForFunction(DifferentialFunction function) {
          val inputs = getInputsForFunction(function);
          if (inputs == null) {
              throw new ND4JIllegalStateException("No inputs found for function " + function);
          }
  
          val vars = new SDVariable[inputs.length];
          for (int i = 0; i < inputs.length; i++) {
              vars[i] = getVariable(inputs[i]);
              if (vars[i] == null) {
                  throw new ND4JIllegalStateException("Found null variable at index " + i);
              }
          }
  
          return vars;
      }