Convert to PDF's Last Page using GraphicsMagick with Python
Future readers of this, if you're experiencing the same dilemma in GraphicsMagick. Here's the easy solution:
Simply write a big number to represent the "last page".
That is: something like:
convert file.pdf[4-99999] +adjoin file%02d.jpg
will work to convert from the 5th pdf page to the last pdf page, into jpgs. 
Note: "+adjoin" & "%02d" have to do with getting all the images rather than just the last. You'll see what i mean if you try it.
To convert a range of say the 1st to 5th page of a multipage pdf into single images is fairly straight forward using:
convert file.pdf[0-4] file.jpg
But how do i convert say the 5th to the last page when i dont know the number of pages in the pdf? 
In ImageMagick "-1"represents the last page, so:
convert file.pdf[4--1] file.jpg works, great stuff,
but it doesnt work in GraphicsMagick.
Is there a way of doing this easily or do i need to find the number of pages? 
PS: need to use graphicsmagick instead of imagemagick.
Thank you so much in advance.