The content of a GraphObject can be queried in the same way as the content of the project graph by using a context query: (*...*). For instance of you want to find all F on an imported qsm:

public void getAllF(){
 println(graphobject("myTree.qsm").(*F*));
}

This works at any place where a normal context query would work as well e.g. max, mean, selectWhereMin…

The feature can be seen in the query function in examples:graphexplorer/GraphObjectRef