def Gradual_step(x, transition_period=300):
    """
    supplementary function of gradual changes

    Args:
        x: time point
        transition_peirod: length of the transition period

    Returns:
        float: return value
    """
    if x < 0:
        return 0.0
    elif 0 <= x < transition_period:
        return x / transition_period
    else:
        return 1.0