def _get_rep(obj, arg_rep):
    """Return `(rep, imports)` where `rep` = 'Class(args)'` is a call to the
    `obj` constructor.  This is used to represent derived instances of
    builtin types."""
    module = obj.__class__.__module__
    cname = obj.__class__.__name__
    rep = '{}({})'.format(cname, arg_rep)
    return rep, (module, cname, cname)
