private void addArgumentNode(PyExpression arg, ASTNode beforeThis, boolean commaFirst) {
    ASTNode comma = PyElementGenerator.getInstance(getProject()).createComma();
    ASTNode node = getNode();
    ASTNode argNode = arg.getNode();
    if (commaFirst) {
      node.addChild(comma, beforeThis);
      node.addChild(ASTFactory.whitespace(" "), beforeThis);
      node.addChild(argNode, beforeThis);
    }
    else {
      node.addChild(argNode, beforeThis);
      node.addChild(comma, beforeThis);
      node.addChild(ASTFactory.whitespace(" "), beforeThis);
    }
  }
private void addArgumentNode(PyExpression arg, ASTNode beforeThis, boolean commaFirst)