Can someone show me how to use ENTITY:BuildBonePositions() ?

Can someone show me how to use ENTITY:BuildBonePositions() ? It is really the only thing in GMod Lua that I can’t figure out how to use. Lets say that I just want to move the bones of an entity to a certain postion when I spawn it using this function… how would I do that? Whenever I try to use this function for anything, absolutely nothing happens. Please help. Thanks!