How to use the deeks.deepKeysFromList function in deeks

function generateHeading(data) {
    if (options.KEYS) { return promise.resolve(options.KEYS); }

    let keys = key.deepKeysFromList(data);
    
    let uniqueKeys = [];

    // If the user wants to check for the same schema:
    if (options.CHECK_SCHEMA_DIFFERENCES) {
        // Check for a consistent schema that does not require the same order:
        // if we only have one document - then there is no possibility of multiple schemas
        if (keys && keys.length <= 1) {
            return promise.resolve(_.flatten(keys) || []);
        }
        // else - multiple documents - ensure only one schema (regardless of field ordering)
        let firstDocSchema = keys[0],
            schemaDifferences = 0;

        _.each(keys, function (keys) {
            // If there is a difference between the schemas, increment the counter of schema inconsistencies

function getFieldNameList(data) {
        // If keys weren't specified, then we'll use the list of keys generated by the deeks module
        return Promise.resolve(deeks.deepKeysFromList(data, deeksOptions));
    }