Build a small `validate_order(payload)` helper that ties 4 module-1 ideas together: 1. **Required field** — `qty` must be present. 2. **Type check** — `qty` must be int (reject strings, floats, bools). 3. **Value validation** — `qty` must be > 0. 4. **Response shape** — on success return `{"ok": True, "qty": N}`; on failure return `{"ok": False, "error": "<reason>"}`. Fill the `# TODO` blocks. The harness prints results for valid / missing / negative / wrong-type / float cases.