message: Added exists function to imports
diff: @@ -55,9 +55,7 @@ impl Imports {
  /// import_object.get_export("module", "name");
  /// ```
  pub fn get_export(&self, module: &str, name: &str) -> Option<Extern> {
  - if self
  - .map
  - .contains_key(&(module.to_string(), name.to_string()))
  + if self.exists(module, name)
  {
  let ext = &self.map[&(module.to_string(), name.to_string())];
  return Some(ext.clone());
  @@ -65,6 +63,20 @@ impl Imports {
  None
  }
  + /// Returns if an export exist for a given module and name.
  + ///
  + /// # Usage
  + /// ```no_run
  + /// # use wasmer::Imports;
  + /// let mut import_object = Imports::new();
  + /// import_object.exists("module", "name");
  + /// ```
  + pub fn exists(&self, module: &str, name: &str) -> bool {
  + self
  + .map
  + .contains_key(&(module.to_string(), name.to_string()))
  + }
  +
  /// Returns true if the Imports contains namespace with the provided name.
  pub fn contains_namespace(&self, name: &str) -> bool {
  self.map.keys().any(|(k, _)| (k == name))
  