DATA_TYPE CheckCustomData(string name)/ETHEntity

Returns the data type of a given custom variable. If there is no matching data for that name, returns DT_NODATA.

DATA_TYPE dt = entity.CheckCustomData("characterName");
if (dt == DT_NODATA)
    print("no name!");

if (dt != DT_STRING)
    print("It should be a string!");

The DATA_TYPE enum.