def typical_price(data, high_col='High', low_col='Low', close_col='Close'):
    """
    Typical Price
    Source: https://en.wikipedia.org/wiki/Typical_price
    Params:
        data: pandas DataFrame
        high_col: the name of the HIGH values column
        low_col: the name of the LOW values column
        close_col: the name of the CLOSE values column

    Returns:
        copy of 'data' DataFrame with 'typical_price' column added
    """
    data['typical_price'] = (
        data[high_col] + data[low_col] + data[close_col]) / 3
    return data