Convert GO IDs to GO Term record objects. Populate children.

def _populate_terms(self, optobj):
        """Convert GO IDs to GO Term record objects. Populate children."""
        has_relationship = optobj is not None and 'relationship' in optobj.optional_attrs
        # Make parents and relationships references to the actual GO terms.
        for rec in self.values():
            # Given parent GO IDs, set parent GO Term objects
            rec.parents = set([self[goid] for goid in rec._parents])

            # For each parent GO Term object, add it's child GO Term to the children data member
            for parent_rec in rec.parents:
                parent_rec.children.add(rec)

            if has_relationship:
                self._populate_relationships(rec)