human
Here's a good function header given the following:
I wrote the below code

    pos = vf_time.GetPos()
    cur_time = vf_time.GetTime()
    interval = vf_time.GetInterval()
    interval_size = (interval[1] - interval[0])
    max_interval = vf_time.GetMaxInterval()
    max_interval_size = (max_interval[1] - max_interval[0])
    def _DrawGuideLine(timestamp, fmt, transparency=0.0):
        "Draws    a    guide    line    from    current    interval    at    'timestamp'    to    the    max\n                interval.\n                "
        left_ratio = (float((timestamp - interval[0])) / interval_size)
        left_y = int((iphone_dims[1] * (1.0 - left_ratio)))
        right_ratio = (float((timestamp - max_interval[0])) / (max_interval[1] - max_interval[0]))
        right_y = int((iphone_dims[1] * (1.0 - right_ratio)))
        line = [(pos[0], left_y), (iphone_dims[0], right_y)]
        DrawLine(line, line_color, 0.0)
        DrawLabel(datetime.fromtimestamp(timestamp).strftime(fmt), iphone_dims[0], right_y, text_color, font, 0.0)
    def _DrawHorizontalGuideLine(timestamp, fmt, transparency=0.0):
        "Draws    a    guide    line    from    current    interval    at    'timestamp'    to    the    max\n                interval.\n                "
        left_ratio = (float((timestamp - interval[0])) / interval_size)
        left_y = int((iphone_dims[1] * (1.0 - left_ratio)))
        right_ratio = (float((timestamp - max_interval[0])) / (max_interval[1] - max_interval[0]))
        right_y = int((iphone_dims[1] * (1.0 - right_ratio)))
        line = [((iphone_dims[0] - 60), right_y), (iphone_dims[0], right_y)]
        DrawLine(line, line_color, 0.0)
        DrawLabel(datetime.fromtimestamp(timestamp).strftime(fmt), (iphone_dims[0] - 60), right_y, text_color, font, 0.0)
    [_DrawHorizontalGuideLine(x, '%b    %d,    %Y') for x in interval]
    _DrawHorizontalGuideLine(cur_time, '%b    %d,    %Y')
    interval = max_interval
    interval_size = (max_interval[1] - max_interval[0])
    def _DrawIntervalTick(timestamp, fmt, transparency=0.0):
        "Draws    a    guide    label   ...

What's a good function header?
assistant
#Here's a good function header.

def DrawGuides(vf_time):