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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 remove_species(self, species):
 """ Remove all occurrences of several species from a structure. Args: species: Sequence of species to remove, e.g., ["Li", "Na"]. """

        new_sites = []
        species = [get_el_sp(s) for s in species]

        for site in self._sites:
            new_sp_occu = {sp: amt for sp, amt in site.species.items()
                           if sp not in species}
            if len(new_sp_occu) > 0:
                new_sites.append(PeriodicSite(
                    new_sp_occu, site.frac_coords, self._lattice,
                    properties=site.properties))
        self._sites = new_sites