Question: how to extract items from transfer function and other DynamicSystems objects?

Here is one example:

zeros :=[-1,-2]:
poles :=[0,-4,-6]:
gain  :=5:
sys   :=DS:-TransferFunction(zeros,poles,gain):

now sys above is a transfer function "object". But how would one go about extracting its properties? For example, I'd like to read the actual rational polynomial in s that represents the transfer function, which is embedded inside this oject, but I am not able to find an API to read it. I can only print it to the screen :


But I'd like to assign the  "tf" printed above (the rational polynomial) into a seaprate variable, so I can extract the numerator and denominator if I want to. I have looked and not able to see a way to read this out. I just started learning this package.

Any idea how to look into these system objects? This does nothing:


Using Maple 18. I am looking for a programmable approach, using code. Not a click and point and menu based solution.


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