Json-serializable dict representation of CompletePhononDos.

def as_dict(self):
        """
        Json-serializable dict representation of CompletePhononDos.
        """
        d = {"@module": self.__class__.__module__,
             "@class": self.__class__.__name__,
             "structure": self.structure.as_dict(),
             "frequencies": list(self.frequencies),
             "densities": list(self.densities),
             "pdos": []}
        if len(self.pdos) > 0:
            for at in self.structure:
                d["pdos"].append(list(self.pdos[at]))
        return d