@Override
    public final boolean contains(Object key) {
        return findIndexOfEqualElement(key) != INVALID_INDEX;
    }
Returns true if there is at least one element e in the collection such
that key.elementKeysAreEqual(e) and key.hashCode() == e.hashCode().

@param key       The object to try to match.
clients/src/main/java/org/apache/kafka/common/utils/ImplicitLinkedHashCollection.java