code: def size(self):
          '''Return the number of links in the model'''
          cur = self._conn.cursor()
          querystr = "SELECT COUNT(*) FROM relationship;"
          cur.execute(querystr)
          result = cur.fetchone()
          return result[0f size(self):
          '''Return the number of links in the model'''
          cur = self._conn.cursor()
          querystr = "SELECT COUNT(*) FROM relationship;"
          cur.execute(querystr)
          result = cur.fetchone()
          return result[0]
docs: Return the number of links in the model