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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 from_composition_and_entries(comp, entries_in_chemsys, working_ion_symbol="Li"):
 """ Convenience constructor to make a ConversionElectrode from a composition and all entries in a chemical system. Args: comp: Starting composition for ConversionElectrode, e.g., Composition("FeF3") entries_in_chemsys: Sequence containing all entries in a chemical system. E.g., all Li-Fe-F containing entries. working_ion_symbol: Element symbol of working ion. Defaults to Li. """

        pd = PhaseDiagram(entries_in_chemsys)
        return ConversionElectrode.from_composition_and_pd(comp, pd,
                                                           working_ion_symbol)