def METHOD_NAME(x: Union[List, np.ndarray, pd.Series], y: Union[List, np.ndarray, pd.Series]) -> \
        float:
    """
    Calculate the symmetric Theil's U correlation of y to x.
    Parameters
    ----------
    x: Union[List, np.ndarray, pd.Series]
        A sequence of a categorical variable values without nulls
    y: Union[List, np.ndarray, pd.Series]
        A sequence of a categorical variable values without nulls
    Returns
    -------
    float
        Representing the symmetric Theil U correlation between y and x
    """
    h_x = entropy(value_frequency(x))
    h_y = entropy(value_frequency(y))
    u_xy = theil_u_correlation(x, y)
    u_yx = theil_u_correlation(y, x)  # pylint: disable=arguments-out-of-order
    u_sym = (h_x * u_xy + h_y * u_yx) / (h_x + h_y)
    return u_sym