<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_items(self, gos):
 """Given GO terms, return genes or gene products for the GOs."""

        items = []
        for go_id in gos:
            items.extend(self.go2items.get(go_id, []))
        return set(items)