public ConsumerGroupMember staticMember(String instanceId) {
        String existingMemberId = staticMemberId(instanceId);
        return existingMemberId == null ? null : getOrMaybeCreateMember(existingMemberId, false);
    }
Gets a static member.

@param instanceId The group instance id.

@return The member corresponding to the given instance id or null if it does not exist
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/modern/consumer/ConsumerGroup.java