$_ = $self->_get_vertex( $_ ) foreach @args;

    # @important is a list of argument positions that are 
    # not null (e.g, undef, empty string, or '_')
    my $a = shift @important;
    while( my $z = shift @important ) {
        return if !$self->_check_path($predicate_id,$a,$z,@args[$a,$z]);
        $a = $z;
    }
    return 1;