Extension dependencies not satisfied on `az extension add`

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We're developing the extension for the Wandisco.Fusion resource provider and are having an issue with one of our extensions listed dependencies not being satisfied

**Describe the bug**

We're trying to make use of the azure-mgmt-resourcegraph package in our extension to check ARG, this dependency is listed in `setup.py`.

When we build our .whl extension and install with pip the dependency is satisfied.
Installing the same .whl through `az extension add --source` does not satisfy the dependency. Wondering if perhaps this dependency is restricted in Azure CLI because it's an azure package?

**To Reproduce**
NA

**Expected behavior**
Dependencies listed in setup.py for our extension are satisfied when the extension is added to azure-cli

**Environment summary**
OS: Mac/10.14.6
CLI: 2.28.1
Shell: bash
Install: `az extension add --source`

**Additional context**
NA