def find_expired(bucket_items, now):
    """
    If there are no expired items in the bucket returns
    empty list

    >>> bucket_items = [('k1', 1), ('k2', 2), ('k3', 3)]
    >>> find_expired(bucket_items, 0)
    []
    >>> bucket_items
    [('k1', 1), ('k2', 2), ('k3', 3)]

    Expired items are returned in the list and deleted from
    the bucket

    >>> find_expired(bucket_items, 2)
    ['k1']
    >>> bucket_items
    [('k2', 2), ('k3', 3)]
    """
    expired_keys = []
    for i in range(len(bucket_items) - 1, -1, -1):
        key, expires = bucket_items[i]
        if expires < now:
            expired_keys.append(key)
            del bucket_items[i]
    return expired_keys