function id2msg( id ) {
	if ( !isString( id ) ) {
		throw new TypeError( format( 'invalid argument. Must provide a string. Value: `%s`.', id ) );
	}
	if ( !db ) {
		db = database();
	}
	if ( hasOwnProp( db, id ) ) {
		return db[ id ];
	}
	return null;
}
Returns an error message corresponding to a provided two-character error identifier.

@param {string} id - error identifier
@throws {TypeError} must provide a string
@returns {(string|null)} error message

@example
var v = id2msg( '9b' );
// returns <string>

@example
var v = id2msg( 'boop' );
// returns null