internal utils for roxygen tags reuse
a 'flextable' object, see flextable-package to learn how to create 'flextable' object.
row selector, see section Row selection with the i parameter
in <Selectors in flextable>.
column selector, see section Column selection with the j parameter
in <Selectors in flextable>.
part selector, see section Part selection with the part
parameter in <Selectors in flextable>.
Value 'all' can be used.