@return true if this map contains a mapping for the specified key
@param key key whose presence in this map is to be tested
file : https_github_com_apache_commons-collections_git/src/main/java/org/apache/commons/collections4/bidimap/TreeBidiMap.java
file : https_github_com_apache_commons-collections_git/src/main/java/org/apache/commons/collections4/MultiValuedMap.java