function isDirective(node) {
			return (
				node.type === "ExpressionStatement" &&
				node.expression.type === "Literal" &&
				typeof node.expression.value === "string" &&
				!astUtils.isParenthesised(sourceCode, node.expression)
			);
		}
Checks whether or not a given node is a directive.
The directive is a `ExpressionStatement` which has only a string literal not surrounded by
parentheses.
@param {ASTNode} node A node to check.
@returns {boolean} Whether or not the node is a directive.
@private