Add new blog posts to my Buffer queue

import xml.etree.ElementTree as ET
from clickruntime import on_trigger, credentials, http, notify, state, report_fetched

FEED = "https://blog.example.com/feed"
CHANNEL_IDS = ["linkedin-channel-id", "x-channel-id"]  # from Buffer's channels query

def buffer(query, variables=None):
    resp = http.post("https://api.buffer.com", json={"query": query, "variables": variables or {}},
                     headers={"Authorization": f"Bearer {credentials.secret('BUFFER_API_KEY')}"})
    resp.raise_for_status()
    return resp.json()["data"]

@on_trigger
def run(event):
    root = ET.fromstring(http.get(FEED).content)
    items = [(i.findtext("guid") or i.findtext("link"), i.findtext("title"), i.findtext("link"))
             for i in root.iter("item")]
    seen = state.get("seen")
    if seen is None:  # first run: remember what's there, don't flood the queue
        state.set("seen", [i[0] for i in items])
        return {"queued": 0}
    new = [i for i in items if i[0] not in seen]
    report_fetched(len(new))
    for _, title, link in reversed(new):
        for ch in CHANNEL_IDS:
            buffer("mutation($input: CreatePostInput!) { createPost(input: $input) { ... on PostActionSuccess { post { id } } "
                   "... on MutationError { message } } }",
                   {"input": {"channelId": ch, "text": f"{title}\n{link}", "schedulingType": "automatic", "mode": "addToQueue"}})
    if new:
        notify.email_me(f"{len(new)} blog post{'s' if len(new) > 1 else ''} added to Buffer",
                        "\n\n".join(f"\"{t}\"\n{l}" for _, t, l in new) +
                        "\n\nBuffer will publish each in the next open slot for each channel.")
    state.set("seen", (seen + [i[0] for i in new])[-500:])
    return {"queued": len(new)}