def block_sep0(self, Y):
        r"""Separate variable into component corresponding to
        :math:`\mathbf{y}_0` in :math:`\mathbf{y}\;\;`.
        """

        # This method is overridden because we have to change the
        # mechanism for combining the Y0 and Y1 blocks into a single
        # array (see comment in the __init__ method).
        shp = Y.shape[0:self.cri.axisC] + self.y0shp[self.cri.axisC:]
        return Y[(slice(None),)*self.cri.axisC +
                 (slice(0, self.y0I),)].reshape(shp)
r"""Separate variable into component corresponding to
        :math:`\mathbf{y}_0` in :math:`\mathbf{y}\;\;`.