Hello, Is it feasible to use an environment variable in

credentials

parameter in code below?

flow.from_source(
        source=GitRepository(
        url=code_url,
        branch=branch_name,
        credentials={"access_token": Secret.load("github-access-token")}),
        entrypoint=entry_point
    ).deploy(
        name=deployment_name,
        work_pool_name=work_pool,
        tags=tags,
        version=deployment_version,
        parameters=parameters
    )

There are 3 types of parameters what I can supply for

credentials

parameter. I would like to use dictionary type of the parameter with

$GITHUB_TOKEN

environment variable but it's generates an error. The code below doesn't work.

flow.from_source(
        source=GitRepository(
        url=code_url,
        branch=branch_name,
        credentials={"username": "prefect", "access_token": "$GITHUB_TOKEN"}),
        entrypoint=entry_point
    ).deploy(
        name=deployment_name,
        work_pool_name=work_pool,
        tags=tags,
        version=deployment_version,
        parameters=parameters
    )

Error message: ValueError: Please save your access token as a Secret block before converting this storage object to a pull step. Thank you.