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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 replace(self, i, species, coords=None, coords_are_cartesian=False, properties=None):
 """ Replace a single site. Takes either a species or a dict of species and occupations. Args: i (int):
 Index of the site in the _sites list. species (species-like):
 Species of replacement site coords (3x1 array):
 Coordinates of replacement site. If None, the current coordinates are assumed. coords_are_cartesian (bool):
 Whether coordinates are cartesian. Defaults to False. properties (dict):
 Properties associated with the site. """

        if coords is None:
            frac_coords = self[i].frac_coords
        elif coords_are_cartesian:
            frac_coords = self._lattice.get_fractional_coords(coords)
        else:
            frac_coords = coords

        new_site = PeriodicSite(species, frac_coords, self._lattice,
                                properties=properties)
        self._sites[i] = new_site