Insert some values into a bi-temporal dataframe.
        This is like what would happen when we get a price correction.

def insert_at(df, sample_date, values):
    """ Insert some values into a bi-temporal dataframe.
        This is like what would happen when we get a price correction.
    """
    observed_dt = dt(datetime.now())
    return multi_index_insert_row(df, [sample_date, observed_dt], values)