code: public static <E> Map<Integer, E> indexed(Iterable<E> self) {
          return indexed(self, 0);
      }
docs: Zips an Iterable with indices in (index, value) order.
  <p/>
  Example usage:
  <pre class="groovyTestCase">
  assert [0: "a", 1: "b"] == ["a", "b"].indexed()
  assert ["0: a", "1: b"] == ["a", "b"].indexed().collect { idx, str {@code ->} "$idx: $str" }
  </pre>
  
  @param self an Iterable
  @return a zipped map with indices
  @see #withIndex(Iterable)
  @since 2.4.0