def set_value(dictionary, keys, value):
    """
    Similar to Python's built in `dictionary[key] = value`,
    but takes a list of nested keys instead of a single key.
    set_value({'a': 1}, [], {'b': 2}) -> {'a': 1, 'b': 2}
    set_value({'a': 1}, ['x'], 2) -> {'a': 1, 'x': 2}
    set_value({'a': 1}, ['x', 'y'], 2) -> {'a': 1, 'x': {'y': 2}}
    """
    if not keys:
        dictionary.update(value)
        return
    for key in keys[:-1]:
        if key not in dictionary:
            dictionary[key] = {}
        dictionary = dictionary[key]
    dictionary[keys[-1]] = value
