Bounds for parameters in `paramsarray`.

def paramsarraybounds(self):
        """Bounds for parameters in `paramsarray`."""
        bounds = []
        for (i, param) in self._index_to_param.items():
            if isinstance(param, str):
                bounds.append(self.model.PARAMLIMITS[param])
            elif isinstance(param, tuple):
                bounds.append(self.model.PARAMLIMITS[param[0]])
            else:
                raise ValueError("Invalid param type")
        bounds = [(tup[0] + ALMOST_ZERO, tup[1] - ALMOST_ZERO) for tup in bounds]
        assert len(bounds) == len(self._index_to_param)
        return tuple(bounds)