assert mapto != "", "%s: must specify mapto in context %s, id '%s'" % (filename, context, id)
assert id != "", "%s: must specify id in context %s, mapto '%s'" % (filename, context, mapto)
assert flags != 0, "%s: must specify at least one flag in context %s, id '%s'" % (filename, context, id)
assert mapto != "", "%s: must specify mapto in context %s, id '%s'" % (filename, context, id)
assert id != "", "%s: must specify id in context %s, mapto '%s'" % (filename, context, mapto)
assert flags != 0, "%s: must specify at least one flag in context %s, id '%s'" % (filename, context, id)