def METHOD_NAME(
    self, log: DataFrame, users: DataFrame
) -> DataFrame:
    """Implementations of this method must return a dataframe with user vectors.
    User vectors from this method are used to infer the index.
    Args:
        log: DataFrame with interactions
        users: DataFrame with users
    Returns: DataFrame[user_idx int, vector array<double>] or DataFrame[vector array<double>].
    Vector column name in dataframe can be anything.
    """