def is_new_span(self, citation_id, start, end):
        """Check if a span is new and mark it as seen."""
        span = (citation_id, start, end)
        if span in self.seen_spans:
            return False
        self.seen_spans.add(span)
        return True
Check if a span is new and mark it as seen.
py/tests/unit/agent/test_streaming_agent.py