Add optimization rule for subgraph prerequisite entity

Issue

I want to load a subgraph, roughly defined as:

%YAML1.2
---
prerequisites:
 - name: format
---
components:
 - name: client
   parameters:
      format: prerequisites/format

in another graph, also roughly defined as:

%YAML1.2
---
name: config
components:
 - name: format
   # type, parameters, etc.
---
components:
 - type: nvidia::gxf::Subgraph
   parameters:
      location: <path/to/subgraph.yaml>
      prerequisites:
         format: config/format

As you can see, I am trying to pass a component of another entity as a prerequisite of the subgraph.
For the gxf optimizer to work I have to define a proper optimization rule in the namespace injector rule file:

%YAML 1.2
---
operation: namespace_injector
body:
  components:
    - type: nvidia::gxf::Subgraph
      path_parameter_keys: [ <???> ]

Issue

What is the syntax to define an optimization rule for the prerequisite component parameter?
I have tried:

• prerequisites.format
• prerequisites/format
• prerequisites: [ format ]
• prerequisites
• format

and none of them provided the desired result.

Start with the namespace injector rule file and the nvidia::gxf::Subgraph entry shown in the issue; compare how path_parameter_keys is defined for prerequisite component parameters. Confirm the accepted key syntax by checking the optimizer's handling of the prerequisites parameter, then verify that config/format resolves to the subgraph's prerequisite.