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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 gettrace(self, burn=0, thin=1, chain=-1, slicing=None):
 """Return the trace. :Stochastics: - burn (int):
 The number of transient steps to skip. - thin (int):
 Keep one in thin. - chain (int):
 The index of the chain to fetch. If None, return all chains. - slicing: A slice, overriding burn and thin assignement. """

        if slicing is None:
            slicing = slice(burn, None, thin)
        if chain is not None:
            if chain < 0:
                chain = range(self.db.chains)[chain]
            return self._trace[chain][slicing]
        else:
            return concatenate(list(self._trace.values()))[slicing]