code: public CollectionAssert hasFlattenedSizeBetween(int lowerBound, int higherBound) {
  		isNotNull();
  		int flattenedSize = flattenedSize(0, this.actual);
  		if (!(flattenedSize >= lowerBound && flattenedSize <= higherBound)) {
  			failWithMessage("The flattened size <%s> is not between <%s> and <%s>",
  					flattenedSize, lowerBound, higherBound);
  		}
  		return this;
  	}
docs: Flattens the collection and checks whether size is between the provided value.
  @param lowerBound - the flattened collection should have size greater than or equal
  to this value
  @param higherBound - the flattened collection should have size less than or equal
  to this value
  @return this