Return a string representation of the Wilson coefficients `C_out`
        in WCxf format. If `stream` is specified, export it to a file.
        `fmt` defaults to `yaml`, but can also be `json`.

        Note that the Wilson coefficients are rotated into the Warsaw basis
        as defined in WCxf, i.e. to the basis where the down-type and charged
        lepton mass matrices are diagonal.

def dump_wcxf(self, C_out, scale_out, fmt='yaml', stream=None, **kwargs):
        """Return a string representation of the Wilson coefficients `C_out`
        in WCxf format. If `stream` is specified, export it to a file.
        `fmt` defaults to `yaml`, but can also be `json`.

        Note that the Wilson coefficients are rotated into the Warsaw basis
        as defined in WCxf, i.e. to the basis where the down-type and charged
        lepton mass matrices are diagonal."""
        wc = self.get_wcxf(C_out, scale_out)
        return wc.dump(fmt=fmt, stream=stream, **kwargs)