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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_species(self, species_mapping):
 """ Swap species. Args: species_mapping (dict):
 dict of species to swap. Species can be elements too. E.g., {Element("Li"):
 Element("Na")} performs a Li for Na substitution. The second species can be a sp_and_occu dict. For example, a site with 0.5 Si that is passed the mapping {Element('Si):
 {Element('Ge'):
0.75, Element('C'):
0.25} } will have .375 Ge and .125 C. """


        species_mapping = {get_el_sp(k): v
                           for k, v in species_mapping.items()}
        sp_to_replace = set(species_mapping.keys())
        sp_in_structure = set(self.composition.keys())
        if not sp_in_structure.issuperset(sp_to_replace):
            warnings.warn(
                "Some species to be substituted are not present in "
                "structure. Pls check your input. Species to be "
                "substituted = %s; Species in structure = %s"
                % (sp_to_replace, sp_in_structure))

        for site in self._sites:
            if sp_to_replace.intersection(site.species):
                c = Composition()
                for sp, amt in site.species.items():
                    new_sp = species_mapping.get(sp, sp)
                    try:
                        c += Composition(new_sp) * amt
                    except Exception:
                        c += {new_sp: amt}
                site.species = c