Lab 1: Exploring & Detecting PII

Implement PII detection and redaction over free text.

Complete two functions in the notebook:

• detect_pii(text) -> set[str] — return the set of PII labels present, drawn from {"EMAIL", "SSN", "PHONE"}.
• redact_pii(text) -> str — return the text with every detected PII value replaced by [REDACTED].

Use the in-browser playground to iterate, then Submit for authoritative grading in the sandbox. Hidden checks verify detection accuracy, false-positive behavior, and redaction.