How can I call FISH function by using ""?

In the Itasca common API, the following function is provided but I cannot find an appropriate example.

Itasca FISH module. string[,(tuple: any)]) → Any.
Call FISH function func return result.

I tried to get mechanical total time by using the Python command as below, but it gives error “FISH symbol is not defined”

mt =‘’)

It call an user defined fish function. why don’t use it.mech_age?

Thank you for your answer, Huy.

I’ll try it.mech_age.