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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 pos(self):
 """A dictionary of the current walker positions. If the sampler hasn't been run yet, returns p0. """

        pos = self._pos
        if pos is None:
            return self.p0
        # convert to dict
        pos = {param: self._pos[..., k]
               for (k, param) in enumerate(self.sampling_params)}
        return pos