How to Control a Multi-layered Agent's Sub Sequencer Using a Top Level Virtual Sequencer

Hello Everyone,

I am trying to control a sub virtual sequencer's non-virtual sub sequencers using a top level virtual sequencer.
It looks like this diagram.

<start of diagram>

                       .------------------------------------------------------.
                       | my_test                                              
                       | .--------------------------------------------------. |
                       | | sequences                                        | |
                       | '--------------------------------------------------' |
                       | .--------------------------------------------------. |
                       | | my_env                                           | |
                       | '--------------------------------------------------' |
                       '/----------------------------------------------------\'
                       /                                                      \
                      /                                                        \
                     /                                                          \
                    /                                                            \
                   /                                                              \
                  /                                                                \
                 /                                                                  \
                /                                                                    \
               /                                                                      \
              /                                                                        \
             /                                                                          \
            /                                                                            \
           /                                                                              \
          /                                                                                \
         /                                                                                  \
        /                                                                                    \
       /                                                                                      \
      /                                                                                        \
     /                                                                                          \
    /                                                                                            \
   /                                                                                              \
  /                                                                                                \
 /                                                                                                  \
.----------------------------------------------------------------------------------------------------.
| my_env                                                                                             |
|                                     .------------------------.                                     |
|                                     | my_virtual_sequencer   |                                     |
|                                     '------------------------'                                     |
| .-----------------------------------. .----------------------------. .---------------------------. |
| | sub_virtual_agent                 | | sub_agent_a                | | sub_agent_b               | |
| | .-------------------------------. | | .------------------------. | | .-----------------------. | |
| | | sub_virtual_sequencer         | | | | sub_sequencer_a        | | | | sub_sequencer_b       | | |
| | '-------------------------------' | | '------------------------' | | '-----------------------' | |
| |       .-------------------------. | | .------------------------. | | .-----------------------. | |
| |       | sub_agent_3             | | | | driver_a               | | | | driver_b              | | |
| |     .-------------------------. | | | '------------------------' | | '-----------------------' | |
| |     | sub_agent_2             | | | | .------------------------. | | .-----------------------. | |
| | .---------------------------. | | | | | monitor_a              | | | | monitor_b             | | |
| | | sub_agent_1               | | | | | '------------------------' | | '-----------------------' | |
| | | .-----------------------. | | | | '----------------------------' '---------------------------' |
| | | | sub_sequencer_1       | | | | |                                                              |
| | | '-----------------------' | | | |                                                              |
| | | .-----------------------. | | | |                                                              |
| | | | driver_1              | | | | |                                                              |
| | | '-----------------------' | | | |                                                              |
| | | .-----------------------. | | | |                                                              |
| | | | monitor_1             | | |-' |                                                              |
| | | '-----------------------' |-'   |                                                              |
| | '---------------------------'     |                                                              |
| '-----------------------------------'                                                              |
'----------------------------------------------------------------------------------------------------'

<end of diagram>

I am trying to apply section 4.8 Virtual Sequences of uvm users guide.
But I think I am missing on something.

I have a top level virtual sequence that has the top level virtual sequencer as its p_sequencer. I have this in the macro:

`uvm_declare_p_sequencer(my_virtual_sequencer)

And then I have this in the task body() to access the sub sequencer of the sub virtual sequencer:

`uvm_do_on(sub_sequence_1, p_sequencer.i_sub_virtual_sequencer.i_sub_sequencer_1);

sub_sequence_1 is a physical sequence.
Is this correct under the UVM standard?
If not, how do I properly control i_sub_sequencer_1?

This is how I access it in the test build_phase:

uvm_config_db #(uvm_object_wrapper)::set(this, "i_my_env,i_my_virtual_sequencer.main_phase","default_sequence",my_virtual_sequence::type_id::get());

Any help/inputs to this is much appreciated.

Thanks,
Martin