message: Add HeaderMap is_empty method
diff: @@ -64,6 +64,10 @@ impl HeaderMap {
  pub fn new() -> Self {
  HeaderMap::default()
  }
  +
  + pub fn is_empty(&self) -> bool {
  + self.inner.is_empty()
  + }
  }
  impl HeaderMap {
  @@ -308,4 +312,15 @@ mod tests {
  println!("bytes: {:?}", from_utf8(&bytes));
  }
  +
  + #[test]
  + fn is_empty() {
  + let mut headers = HeaderMap::new();
  + assert!(headers.is_empty());
  +
  + headers.append("Key", "value");
  + headers.append("Key", "second_value");
  + headers.insert("Second", "SecondValue");
  + assert!(!headers.is_empty());
  + }
  }
  