code: def _push_condition(predicate):
      
      global _depth
      _check_under_condition()
      _depth += 1
      if predicate is not otherwise and len(predicate) > 1:
          raise PyrtlError('all predicates for conditional assignments must wirevectors of len 1')
      _conditions_list_stack[-1].append(predicate)
      _conditions_list_stack.append([])
docs: As we enter new conditions, this pushes them on the predicate stack.