code: public static void eachCombination(Iterable self, Closure<?> function) {
          each(GroovyCollections.combinations(self), function);
      }
docs: Applies a function on each combination of the input lists.
  <p>
  Example usage:
  <pre class="groovyTestCase">[[2, 3],[4, 5, 6]].eachCombination { println "Found $it" }</pre>
  
  @param self a Collection of lists
  @param function a closure to be called on each combination
  @see groovy.util.GroovyCollections#combinations(Iterable)
  @since 2.2.0