code: func (t *Table) InsertColumn(column int) *Table {
  	for row := range t.cells {
  		if column >= len(t.cells[row]) {
  			continue
  		}
  		t.cells[row] = append(t.cells[row], nil)             // Extend by one.
  		copy(t.cells[row][column+1:], t.cells[row][column:]) // Shift to the right.
  		t.cells[row][column] = &TableCell{}                  // New element is an uninitialized table cell.
  	}
  	return t
  }
docs: // InsertColumn inserts a column before the column with the given index. Cells
  // in the given column and to its right will be shifted to the right by one
  // column. Rows that have fewer initialized cells than "column" will remain
  // unchanged.