<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _stub_tag(constructor, node):
 """Stub a constructor with a dictionary."""

    seen = getattr(constructor, "_stub_seen", None)

    if seen is None:
        seen = constructor._stub_seen = set()

    if node.tag not in seen:
        print("YAML tag {} is not supported".format(node.tag))
        seen.add(node.tag)

    return {}