function isNodeNully (node: ?Node): boolean {
    if (node == null) {
      return true;
    }
    else if (node.type === 'Identifier' && node.name === 'undefined') {
      return true;
    }
    else if (node.type === 'Literal' && node.value === null) {
      return true;
    }
    else if (node.type === 'UnaryExpression' && node.operator === 'void') {
      return true;
    }
    else {
      return false;
    }
  }
Determine whether a given node is nully (null or undefined).