plugins/bem.js
function getKey(propNode) {
    if (propNode.key.type === "Literal") {
        return propNode.key.value;
    }

    if (propNode.key.type === "Identifier") {
        return propNode.key.name;
    }
}
function getKey(propNode) {
    if (propNode.key.type === "Literal") {
        return propNode.key.value;
    }

    if (propNode.key.type === "Identifier") {
        return propNode.key.name;
    }
}
Returns a key value of a property expression
@param {Object} propNode an AST node of a propery expression