Question: about DynamicSystems module and transfer function


I use the module DynamicSystem to transform a state system in transfer functions. Next, i can plot Bode diagram with this module.

However, i have a little problem. I don't manage to extract only one transfer function from a dynamic system when i have several transfer functions (see example below)

I'd like to plot the first transfer function alone in fact. How can i extract y1(s) ?

with( DynamicSystems ): 
a := Matrix([[0, 1,0], [0, -167,878],[0, -53,-6250]]); 
b := Matrix([[0], [0],[1563]]); 
c := Matrix([[1, 0,0], [0, 0,1]]); 
d := Matrix([[0], [0]]); 
sys5 := TransferFunction(a, b, c, d, systemname="Example discrete MIMO system",outputvariable =[y1,y2]): 


Thank you for your help

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