function (data, oldContext, newContext) {
            // this function is called only if the language has changed
            if (newContext.language === undefined) {
                return _.keys(data[oldContext.language]);
            }
            if (oldContext.language === undefined) {
                return _.keys(data[newContext.language]);
            }

            return _.union(_.keys(data[newContext.language]), _.keys(data[oldContext.language]));
        }
function (data, oldContext, newContext) {
            // this function is called only if the language has changed
            if (newContext.language === undefined) {
                return _.keys(data[oldContext.language]);
            }
            if (oldContext.language === undefined) {
                return _.keys(data[newContext.language]);
            }

            return _.union(_.keys(data[newContext.language]), _.keys(data[oldContext.language]));
        }
function ( data , oldContext , newContext ) { // this function is called only if the language has changed if ( newContext . language === undefined ) { return _ . keys ( data [ oldContext . language ] ) ; } if ( oldContext . language === undefined ) { return _ . keys ( data [ newContext . language ] ) ; } return _ . union ( _ . keys ( data [ newContext . language ] ) , _ . keys ( data [ oldContext . language ] ) ) ; }
Determines if there are preference IDs that could change as a result
of the context change. This implementation considers only changes in
language.

@param {Object} data Data in the Scope
@param {{language: string}} oldContext Old context
@param {{language: string}} newContext New context
@return {Array.<string>|undefined} list of preference IDs that could have changed
Determines if there are preference IDs that could change as a result of the context change . This implementation considers only changes in language .
returns a list of all the language keys that have changed