Upper Band.

    Formula:
    ub = cb(t) * (1 + env_percentage)

def upper_band(data, period, env_percentage):
    """
    Upper Band.

    Formula:
    ub = cb(t) * (1 + env_percentage)
    """
    cb = center_band(data, period)
    ub = [val * (1 + float(env_percentage)) for val in cb]
    return ub