code: def attributes_in_restriction(self):
          
          return set(name for name in self.heading.names
                     if re.search(r'\b' + name + r'\b', self.where_clause))
docs: :return: list of attributes that are probably used in the restriction.
              The function errs on the side of false positives.
              For example, if the restriction is "val='id'", then the attribute 'id' would be flagged.
              This is used internally for optimizing SQL statements.