<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _traverse(element, condition=None):
 """ Traversal API intended for debugging. """

        if condition is None or condition(element):
            yield element
        if isinstance(element, DictElement):
            for child in element.values():
                for _ in BaseElement._traverse(child, condition):
                    yield _
        elif isinstance(element, ListElement):
            for child in element:
                for _ in BaseElement._traverse(child, condition):
                    yield _
        elif attr.has(element.__class__):
            for field in attr.fields(element.__class__):
                child = getattr(element, field.name)
                for _ in BaseElement._traverse(child, condition):
                    yield _