'**SUMMARY**
Trims the TrackSet(lists of all the saved objects) to save memory. It is implemented in
Image.track() by default, but if you want to trim the list manually, use this.
**RETURNS**
Nothing.
**EXAMPLE**
>>> while True:
... img1 = cam.getImage()
... ts = img1.track("camshift", ts1, img, bb)
... if len(ts) > 30:
... ts.trimList(10)
... img = img1'

def trimList(self, num):

    ts = self
    for i in range(num):
        ts.pop(0)
