jersey2-guice-impl/src/main/java/com/squarespace/jersey2/guice/BindingUtils.java
private static Key<?> newKey(Type type, Set<? extends Annotation> qualifiers) {
    if (qualifiers.isEmpty()) {
      return Key.get(type);
    }
    
    // There can be only one qualifier.
    if (qualifiers.size() == 1) {
      for (Annotation first : qualifiers) {
        return Key.get(type, first);
      }
    }
    
    return null;
  }
private static Key<?> newKey(Type type, Set<? extends Annotation> qualifiers) {
    if (qualifiers.isEmpty()) {
      return Key.get(type);
    }
    
    // There can be only one qualifier.
    if (qualifiers.size() == 1) {
      for (Annotation first : qualifiers) {
        return Key.get(type, first);
      }
    }
    
    return null;
  }
Creates and returns a {@link Key} for the given {@link Type} and {@link Set} of {@link Annotation}s.