'Return None.  Insert column of stubs at column `loc`.
If there is a header row, it gets an empty cell.
So ``len(stubs)`` should equal the number of non-header rows.'

def insert_stubs(self, loc, stubs):

    _Cell = self._Cell
    stubs = iter(stubs)
    for row in self:
        if (row.datatype == 'header'):
            empty_cell = _Cell('', datatype='empty')
            row.insert(loc, empty_cell)
        else:
            try:
                row.insert_stub(loc, next(stubs))
            except StopIteration:
                raise ValueError('length    of    stubs    must    match    table    length')
