code: public static <T> T isA(Class<T> type) {
          reportMatcher(new InstanceOf(type));
          return defaultValue(type);
      }
docs: <code>Object</code> argument that implements the given class.
  <p>
  See examples in javadoc for {@link ArgumentMatchers} class
  
  @param <T>  the accepted type.
  @param type the class of the accepted type.
  @return <code>null</code>.
  @see #any(Class)