Vertical stacking for tabarrays.

        Stack tabarray(s) in `new` below `self`.

        **See also**

                :func:`tabular.tabarray.tab_rowstack`, 
                :func:`tabular.spreadsheet.rowstack`

def rowstack(self, new, mode='nulls'):
        """
        Vertical stacking for tabarrays.

        Stack tabarray(s) in `new` below `self`.

        **See also**

                :func:`tabular.tabarray.tab_rowstack`, 
                :func:`tabular.spreadsheet.rowstack`

        """
        if isinstance(new,list):
            return tab_rowstack([self] + new, mode)
        else:
            return tab_rowstack([self, new], mode)