use a face to split a solid, how to exactly retrieve the left or right splitted solid

use a face to split a solid, how to exactly retrieve the left or right splitted solid

for example:

BOPAlgo_Builder aBuilder;

aBuilder.AddArgument(solid);
aBuilder.AddArgument(face);
aBuilder.Perform();

//const TopTools_ListOfShape& aSolSplits = aBuilder.Modified(inner_lower_solid);

//_shape = aSolSplits.First();

is there some function to check a solid is in a face' left or right ???