You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: grouping_sets_test.go
    path of file: ./repos/tidb/pkg/expression
    
    the code of the file until where you have to start completion: // Copyright 2022 PingCAP, Inc.
//
// Licens
    
func TestGroupSetsTargetOne(t *testing.T) {
	defer view.Stop()
	a := &Column{
		UniqueID: 1,
	}
	b := &Column{
		UniqueID: 2,
	}
	c := &Column{
		UniqueID: 3,
	}
	d := &Column{
		UniqueID: 4,
	}
	// non-merged group sets
	//	1: group sets {<a,b>}, {<c>} when the normal agg(d), d can occur in either group of <a,b> or <c> after tuple split. (normal column are appended)
	//  2: group sets {<a,b>}, {<c>} when the normal agg(c), c can only be found in group of <c>, since it will be filled with null in group of <a,b>
	//  3: group sets {<a,b>}, {<c>} when the normal agg with multi col args, it will be a little difficult, which is banned in canUse3Stage4MultiDistinctAgg by now.
	newGroupingSets := make(GroupingSets, 0, 3)
	groupingExprs1 := []Expression{a, b}
	groupingExprs2 := []Expression{c}
	newGroupingSets = append(newGroupingSets, GroupingSet{groupingExprs1})
	newGroupingSets = append(newGroupingSets, GroupingSet{groupingExprs2})

	targetOne := []Expression{d}
	offset := newGroupingSets.TargetOne(targetOne)
	require.NotEqual(t, offset, -1)
	require.Equal(t, offset, 0) // <a,b> and <c> both ok

	targetOne = []Expression{c}
	offset = newGroupingSets.TargetOne(targetOne)
	require.NotEqual(t, offset, -1)
	require.Equal(t, offset, 1) // only <c> is ok

	targetOne = []Expression{b}
	offset = newGroupingSets.TargetOne(targetOne)
	require.NotEqual(t, offset, -1)
	require.Equal(t, offset, 0) // only <a,b> is ok

	targetOne = []Expression{a}
	offset = newGroupingSets.TargetOne(targetOne)
	require.NotEqual(t, offset, -1)
	require.Equal(t, offset, 0) // only <a,b> is ok

	targetOne = []Expression{b, c}
	offset = newGroupingSets.TargetOne(targetOne)
	require.Equal(t, offset, -1) // no valid one can be found.

	// merged group sets
	// merged group sets {<a>, <a,b>} when the normal agg(d),
	// from prospect from data grouping, we need keep the widest grouping layout <a> when trying
	// to shuffle data targeting for grouping layout {<a>, <a,b>}; Additional, since column b
	// hasn't been pre-agg or something because current layout is <a>, we should keep all the
	// complete rows until to the upper receiver, which means there is no agg/group operator before
	// shuffler take place.
}