xfrm.py

import sys

hosts = {}

for line in sys.stdin:
    line = line.strip()
    if not line:
        continue
    host, pkg = line.split()
    hosts.setdefault(pkg, set())
    hosts[pkg].add(host)

for pkg in hosts:
    first = True
    for host in hosts[pkg]:
        init = f'{pkg}: '
        print(f'{init if first else " "*len(init)}{host}')
        first = False
    print()