'Get the rows with indices start through end. If target is not provided
memory for a new matrix will be allocated.'

def get_row_slice(self, start, end, target=None):

    width = self.shape[1]
    if (not target):
        target = empty(((end - start), width))
    err_code = _eigenmat.get_row_slice(self.p_mat, target.p_mat, ct.c_int(start), ct.c_int(end))
    if err_code:
        raise generate_exception(err_code)
    return target
