code: public static <T> Collection<T> unique(Collection<T> self) {
          return unique(self, true);
      }
docs: Modifies this collection to remove all duplicated items, using Groovy's
  default number-aware comparator.
  <pre class="groovyTestCase">assert [1,3] == [1,3,3].unique()</pre>
  
  @param self a collection
  @return the now modified collection
  @see #unique(Collection, boolean)
  @since 1.0