Map between numpy and state dtypes

def _setup_dtype(self):
        """Map between numpy and state dtypes"""
        if self._dtype is not None:
            return self._dtype

        dtype = []  # Convert struct data types to numpy data type
        for i, typ in enumerate(self.typlist):
            if typ in self.NUMPY_TYPE_MAP:
                dtype.append(('s' + str(i), self.byteorder +
                              self.NUMPY_TYPE_MAP[typ]))
            else:
                dtype.append(('s' + str(i), 'S' + str(typ)))
        dtype = np.dtype(dtype)
        self._dtype = dtype

        return self._dtype