code: public static <K> Matcher<Map<? extends K, ?>> hasSameKeySet(final Map<? extends K, ?> comparisonMap) {
          return IsMapWithSameKeySet.hasSameKeySet(comparisonMap);
      }
docs: Creates a matcher for {@link Map}s matching when the examined {@link Map} has exactly the same key set of the
  given map. For example:
  <p>
  <pre>assertThat(myMap, hasSameKeySet(anotherMap))</pre>