code: public int sizeOfIn(String expr, Map<String, Object> map) {
          return getMapHelper().sizeOfIn(expr, map);
      }
docs: Determines size of either (Map or Collection) value in the map.
  @param expr expression indicating which (possibly nested) value in the map to determine size of.
  @param map map to find value in.
  @return size of value.
  @throws SlimFixtureException if the value found is not a Map or Collection.