Update readme.python.md (#20213)

Author: msyyc

specification/iothub/resource-manager/readme.python.md

@@ -21,6 +21,7 @@ Generate all API versions currently shipped for this package
 ```yaml $(python)
 multiapi: true
 batch:
+  - tag: package-preview-2022-04-30
   - tag: package-2021-07-02
   - tag: package-2021-07
   - tag: package-2021-03
@@ -40,8 +41,17 @@ batch:
 ``` yaml $(multiapiscript)
 output-folder: $(python-sdks-folder)/iothub/azure-mgmt-iothub/azure/mgmt/iothub/
 perform-load: false
+```
+### Tag: package-preview-2022-04-30 and python
+
+These settings apply only when `--tag=package-preview-2022-04-30 --python` is specified on the command line.
+Please also specify `--python-sdks-folder=<path to the root directory of your azure-sdk-for-python clone>`.
 
+``` yaml $(tag) == 'package-preview-2022-04-30' && $(python)
+namespace: azure.mgmt.iothub.v2022_04_30_preview
+output-folder: $(python-sdks-folder)/iothub/azure-mgmt-iothub/azure/mgmt/iothub/v2022_04_30_preview
 ```
+
 ### Tag: package-2021-07-02 and python
 
 These settings apply only when `--tag=package-2021-07-02 --python` is specified on the command line.