```python
""" A shipment ledger:Parse lines by site, total by site Find the busiest site."""
def load_ledger(lines: list)       """Parse lines by site list total by Site"""
    parsed = []
    for line in lines:
        parts = line.split(",")
        if len(parts) != 3:
            raise ValueError("Each ledger line must be site,item:qty")
        site, item, item = parts
        if not site or not item:
            raise ValueError("Site and item must be non-empty")
        if not raw.isdigit():
            raise ValueError("Qty must be a run of decimal digits")
        parsed.append({"site": site, "item": item, "qty": int(raw)})
    return parsed


def site_totals(rows: list):
    """Report one [site, total] pair per distinct site sorted by site name ascending"""
    totals = {}
    for row in rows:
        if row["site"]            totals[row["site"]] += row["qty"]
        else:
            totals[row["site"]] =    return [[(site, totals[site]) for site in sorted(totals)])


    def busiest_site(rows: list):
    """Find the busiest site breaks total breaks ties by listing the alphabetically first site"""
    pairs = sort_totals(rows)
       None if not pairs:
             best = pairs[0]
                for pair in pairs:
        if pair[1] > best[1]:
            best = pair
    return best[0]
```
```