message: clippy: Fix write/writeln warnings.
diff: @@ -107,7 +107,7 @@ impl<'a, G> Dot<'a, G>
  for node in g.node_references() {
  write!(f, "{}{}", INDENT, g.to_index(node.id()))?;
  if self.config.contains(&Config::NodeIndexLabel) {
  - writeln!(f, "")?;
  + writeln!(f)?;
  } else {
  write!(f, " [label=\"")?;
  node_fmt(node.weight(), &mut |d| Escaped(d).fmt(f))?;
  @@ -123,7 +123,7 @@ impl<'a, G> Dot<'a, G>
  EDGE[g.is_directed() as usize],
  g.to_index(edge.target()))?;
  if self.config.contains(&Config::EdgeNoLabel) {
  - writeln!(f, "")?;
  + writeln!(f)?;
  } else if self.config.contains(&Config::EdgeIndexLabel) {
  writeln!(f, " [label=\"{}\"]", i)?;
  } else {
  @@ -194,7 +194,7 @@ impl<T> fmt::Display for Escaped<T>
  {
  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
  if f.alternate() {
  - write!(&mut Escaper(f), "{:#}\n", &self.0)
  + writeln!(&mut Escaper(f), "{:#}", &self.0)
  } else {
  write!(&mut Escaper(f), "{}", &self.0)
  }
  