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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 to_unit_cell(self, in_place=False):
 """ Move frac coords to within the unit cell cell. """

        frac_coords = np.mod(self.frac_coords, 1)
        if in_place:
            self.frac_coords = frac_coords
        else:
            return PeriodicSite(self.species, frac_coords, self.lattice,
                                properties=self.properties)