Specialize ``self`` to a concrete domain.

def specialize(self, domain):
        """Specialize ``self`` to a concrete domain.
        """
        if domain == self.domain:
            return self

        return type(self)(
            dtype=self.dtype,
            missing_value=self.missing_value,
            dataset=self._dataset.specialize(domain),
            name=self._name,
            doc=self.__doc__,
            metadata=self._metadata,
        )