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### inverse laplace transforms of shifts

I've been trying to get Sage to solve an ODE using Laplace transforms. Unfortunately, shifted functions appear to cause a problem for the inverse_laplace command. David Joyner's ODE book (dated 2008) says that Sage does not have the functionality to do this. Has this situation changed? Do I need to do something differently here to get this to work?

Here is a snippet of something I tried.

u=piecewise([[(0,3),0],[(3,infinity),exp(-2*(t-3))]],t)
u.laplace(t,s)
inverse_laplace(_,s,t)


The first two lines work properly, but the last line returns a formal result:

ilt(e^(-3*s)/(s + 2), s, t)