You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: reflow.rs
    path of file: ./repos/gobang/src/ui
    
    the code of the file until where you have to start completion: use easy_cast::Cast;
use tui::text::StyledGrapheme;
use unicode_segmentation::UnicodeSegmentation;
use unicode_width::UnicodeWidthStr;

const NBSP: &str = "\u{00a0}";

/// A state machine to pack styled symbols into lines.
/// Cannot implement it as Iterator since it yields slices of the internal buffer (need streaming
/// iterators for that).
pub trait LineComposer<'a> {
    fn next_line(&mut self) -> Option<(&[StyledGrapheme<'a>], u16)>;
}

/
    
    fn line_composer_word_wrapper_mixed_length() {
        let width = 20;
        let text = "abcd efghij klmnopabcdefghijklmnopabcdefghijkl mnopab cdefghi j klmno";
        let (word_wrapper, _) = run_composer(Composer::WordWrapper { trim: true }, text, width);
        assert_eq!(
            word_wrapper,
            vec![
                "abcd efghij klmnopab",
                "cdefghijklmnopabcdef",
                "ghijkl mnopab cdefgh",
                "i j klmno"
            ]
        )
    }