private boolean insertGroup(@NonNull final Group group) {
        if (!isGroupExist(group)) {
            this.groups.add(group);
            notifyGroupAdded(group);
            return true;
        }
        throw new IllegalArgumentException("Group already exists");
    }
Adds a group to the existing group list within the network

@param group to be added
@return true if the group was successfully added and false otherwise since a group may already exist with the same group address
@throws IllegalArgumentException if there is no group range allocated or if the address is out of the range allocated to the provisioner
mesh/src/main/java/no/nordicsemi/android/mesh/MeshNetwork.java