Returns the text that is displayed for the closed fold at line {lnum}. Evaluates 'foldtext' in the appropriate context. When there is no closed fold at {lnum} an empty string is returned. {lnum} is used like with |getline()|. Thus "." is the current line, "'m" mark m, etc. Useful when exporting folded text, e.g., to HTML. {not available when compiled without the |+folding| feature} Can also be used as a |method|: GetLnum()->foldtextresult()