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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def trace2array(self, sl):
 """Return an array with the trace of all stochastics, sliced by sl."""

        chain = []
        for stochastic in self.stochastics:
            tr = stochastic.trace.gettrace(slicing=sl)
            if tr is None:
                raise AttributeError
            chain.append(tr)
        return np.hstack(chain)