fn new(format: &str) -> Self {
        UnknownFormatError {
            format: format.into()
        }
    }
/// Make file format error by format name.
Make file format error by format name.
Make file format error by format name .
fn new(format: &str) -> Self {
        UnknownFormatError {
            format: format.into()
        }
    }
fn new ( format : & str ) -> Self { UnknownFormatError { format : format . into ( ) } }
Make file format error by format name.
Make file format error by format name .
format
&str
format
&str