code: def from_merge_origin(cls, tc):
          
          other_tc = tc.tbl.tc(
              tc.row_idx + tc.rowSpan - 1,  # ---other_row_idx
              tc.col_idx + tc.gridSpan - 1  # ---other_col_idx
          )
          return cls(tc, other_tc)
docs: Return instance created from merge-origin tc element.