message: Added contains_key method to Namespace
diff: @@ -189,6 +189,13 @@ impl Namespace {
  {
  self.map.insert(name.into(), Box::new(export))
  }
  +
  + pub fn contains_key<S>(&mut self, key: S) -> bool
  + where
  + S: Into<String>,
  + {
  + self.map.contains_key(&key.into())
  + }
  }
  impl LikeNamespace for Namespace {
  