Sentence:The Milky Way, the [e1]galaxy[/e1] of billions of [e2]stars[/e2] that contains the solar system, has been devouring a much smaller galaxy for hundreds of millions of years, but until now the "dwarf" galaxy had been mistaken for a portion of the Milky Way itself.
 e1: galaxy. 
 e2 : stars.
Answer: Member-Collection(e2,e1)