private Assignment newMemberAssignment(
        GroupAssignment newGroupAssignment,
        String memberId
    ) {
        MemberAssignment newMemberAssignment = newGroupAssignment.members().get(memberId);
        if (newMemberAssignment != null) {
            return new Assignment(newMemberAssignment.partitions());
        } else {
            return Assignment.EMPTY;
        }
    }
Builds the new target assignment.

@return A TargetAssignmentResult which contains the records to update
        the existing target assignment.
@throws PartitionAssignorException if the target assignment cannot be computed.
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/modern/TargetAssignmentBuilder.java