message: Fix class description for Attributes: the instance of the class aren't uniqued, the class has reference semantics.
diff: @@ -61,9 +61,10 @@ class AttributeListStorage;
  /// Attributes are known-constant values of operations and functions.
  ///
  -/// Instances of the Attribute class are immutable, uniqued, immortal, and owned
  -/// by MLIRContext. As such, an Attribute is a POD interface to an underlying
  -/// storage pointer.
  +/// Instances of the Attribute class are references to immutable, uniqued,
  +/// and immortal values owned by MLIRContext. As such, an Attribute is a thin
  +/// wrapper around an underlying storage pointer. Attributes are usually passed
  +/// by value.
  class Attribute {
  public:
  enum class Kind {
  