Piecewise function of several variables and how to display it

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Hi, I need to define a piecewise function of several variables. For a function of one variable I would use probably Piecewise. I would like to work with a function G of two variables t and s that is of this form:

def G(t,s):
    if (t < s):
        return 1
    else:
        return 0

Although this works, I would like to have a nice displaying of this function, like a function generated by Piecewise does. Is there another way how to define this function?