def METHOD_NAME(account_resource_name: Optional[str] = None,
                  extension_resource_name: Optional[str] = None,
                  resource_group_name: Optional[str] = None,
                  opts: Optional[pulumi.InvokeOptions] = None) -> AwaitableGetExtensionResult:
    """
    Gets the details of an extension associated with a Visual Studio Team Services account resource.
    :param str account_resource_name: The name of the Visual Studio Team Services account resource.
    :param str extension_resource_name: The name of the extension.
    :param str resource_group_name: Name of the resource group within the Azure subscription.
    """
    __args__ = dict()
    __args__['accountResourceName'] = account_resource_name
    __args__['extensionResourceName'] = extension_resource_name
    __args__['resourceGroupName'] = resource_group_name
    opts = pulumi.InvokeOptions.merge(_utilities.get_invoke_opts_defaults(), opts)
    __ret__ = pulumi.runtime.invoke('azure-native:visualstudio/v20171101preview:getExtension', __args__, opts=opts, typ=GetExtensionResult).value
    return AwaitableGetExtensionResult(
        id=pulumi.get(__ret__, 'id'),
        location=pulumi.get(__ret__, 'location'),
        name=pulumi.get(__ret__, 'name'),
        plan=pulumi.get(__ret__, 'plan'),
        properties=pulumi.get(__ret__, 'properties'),
        tags=pulumi.get(__ret__, 'tags'),
        type=pulumi.get(__ret__, 'type'))