Oops add missing code

utils/lookup.py

@@ -0,0 +1,32 @@
+import little_boxes.activitypub as ap
+import json
+import requests
+
+import mf2py
+
+
+def lookup(url: str) -> ap.BaseActivity:
+    """Try to find an AP object related to the given URL."""
+    backend = ap.get_backend()
+    resp = requests.get(
+        url,
+        timeout=15,
+        allow_redirects=False,
+        headers={"User-Agent": backend.user_agent()},
+    )
+    resp.raise_for_status()
+
+    # If the page is HTML, maybe it contains an alternate link pointing to an AP object
+    for alternate in mf2py.parse(resp.text).get("alternates", []):
+        if alternate.get("type") == "application/activity+json":
+            return ap.fetch_remote_activity(alternate["url"])
+
+    try:
+        # Maybe the page was JSON-LD?
+        data = resp.json()
+        return ap.parse_activity(data)
+    except json.JSONDecodeError:
+        pass
+
+    # Try content negotiation (retry with the AP Accept header)
+    return ap.fetch_remote_activity(url)