Use assert.Contains to fix btree.TestTreeGet
Use assert.Contains to fix btree.TestTreeGet

jlhonora/go-datastructures,legendtkl/go-datastructures,brianshannan-wf/go-datastructures,jim-slattery-rs/go-datastructures,samklr-ds/go-datastructures,golang-collections/go-datastructures,legendtkl/go-datastructures,Charlesdong/go-datastructures,liufuqiang/go-datastructures,tylertreat/go-datastructures,evanh/go-datastructures,legendtkl/go-datastructures,sdboyer/go-datastructures,lsxia/go-datastructures,Workiva/go-datastructures,Workiva/go-datastructures,tylertreat/go-datastructures,legendtkl/go-datastructures,tomdeering-wf/go-datastructures,Lanzafame/go-datastructures