@throws nullpointerexception if any key or value in {@code multimap} isnull
file : https_github_com_google_guava_git/guava/src/com/google/common/collect/ImmutableSetMultimap.java
file : https_github_com_google_guava_git/guava/src/com/google/common/collect/ImmutableMultimap.java
file : https_github_com_google_guava_git/guava/src/com/google/common/collect/ImmutableListMultimap.java