def _connect_begin_to(self, shape, cxn_pt_idx):
        """
        Add or update a stCxn element for this connector that connects its
        begin point to the connection point of *shape* specified by
        *cxn_pt_idx*.
        """
        cNvCxnSpPr = self._element.nvCxnSpPr.cNvCxnSpPr
        stCxn = cNvCxnSpPr.get_or_add_stCxn()
        stCxn.id = shape.shape_id
        stCxn.idx = cxn_pt_idx
Add or update a stCxn element for this connector that connects its
        begin point to the connection point of *shape* specified by
        *cxn_pt_idx*.