1class DocumentService:
2    
3    ...
4            
5    def update_document_sharing(self, doc_id, user_id, access_level, current_user):
6        # Check if user has admin role or is document owner
7        if not (self.is_document_admin(doc_id, current_user.id) or 
8                self.is_document_owner(doc_id, current_user.id)):
9            return False
10            
11        # Verify target user exists
12        if not self.user_exists(user_id):
13            return False
14            
15        # Update sharing permissions in database
16        success = self.db.execute(
17            "UPDATE doc_access SET access_level = ? WHERE doc_id = ? AND user_id = ?",
18            (access_level, doc_id, user_id)
19        )
20        
21        return success