code: private boolean verifySetCssNameMapping(Node methodName, Node firstArg) {
      DiagnosticType diagnostic = null;
      if (firstArg == null) {
        diagnostic = NULL_ARGUMENT_ERROR;
      } else if (!firstArg.isObjectLit()) {
        diagnostic = EXPECTED_OBJECTLIT_ERROR;
      } else if (firstArg.getNext() != null) {
        Node secondArg = firstArg.getNext();
        if (!secondArg.isString()) {
          diagnostic = EXPECTED_STRING_ERROR;
        } else if (secondArg.getNext() != null) {
          diagnostic = TOO_MANY_ARGUMENTS_ERROR;
        }
      }
      if (diagnostic != null) {
        compiler.report(JSError.make(methodName, diagnostic, methodName.getQualifiedName()));
        return false;
      }
      return true;
    }
docs: Verifies that setCssNameMapping is called with the correct methods.
  
  @return Whether the arguments checked out okay