Update explain feature

[manushak]

Types of changes

• Enhancement (project structure, spelling, grammar, formatting)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

A description of the changes proposed in the Pull Request

[jmcook1186]

Hi @manushak just checked this out and started using it - there's one important behaviour that does not seem to be supported - it's the case where we have two parameters with the same name but different units - this should throw an error, but it seems to overwrite and persist the last-defined version.

e.g. in this manifest there is a deliberately duplicated parameter across two plugins (time-reserved) and I've made the value different from the default hardcoded in the sci-embodied plugin source code. I'd expect explain to detect that the two instances of time-reserved have different units and throw an error.

name: sci-embodied
description: successful path
tags:
initialize:
  plugins:
    "sci-embodied": # a model that calculates m from te, tir, el, rr and rtor
      method: SciEmbodied
      path: "builtin"
    sum:
      method: Sum
      path: "builtin"
      config:
        input-parameters: ["time-reserved", "resources-total"]
        output-parameter: "result"
      parameter-metadata:
        inputs:
          time-reserved:
            description: "carbon emitted due to an application's execution"
            unit: "mins"
            aggregation-method: 'sum'       

explainer: true
tree:
  children:
    child:
      pipeline:
        compute:
          - sci-embodied # duration & config -> embodied
          - sum
      defaults:
        device/emissions-embodied: 1533.120 # gCO2eq
        time-reserved: 3600 # 1hr in seconds
        device/expected-lifespan: 94608000 # 3 years in seconds
        resources-reserved: 1
        resources-total: 8
      inputs:
        - timestamp: 2023-07-06T00:00
          duration: 3600

The current behaviour is correct only if the units for the two identically named parameters are the same.