[Doc] Find SDK by Azure-cli command (Azure#24123)

* create doc

* Update find_sdk_in_cli_command.md

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doc/dev/find_sdk/find_sdk_in_cli_command.md

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+How to Find the SDK in CLI 
+======
+
+This article aims to provide a guide for customer to find the sdk in Azure CLI.
+
+Find SDK function in cli command is divided into the following steps:
+1. Determine the command module
+2. Search its definition in `command.py`
+3. Find the management client and corresponding SDK
+4. Find the function in Python SDK or Doc
+
+## Determine the command module
+
+Before looking for the SDK, please determine the command module you want to find. You can find it through the keyword in the CLI and the corresponding way [here](https://github.com/Azure/azure-cli/tree/dev/src/azure-cli/azure/cli/command_modules).
+
+Such as, if you want to find the module about `az resource group create`, you could find [`resource` folder](https://github.com/Azure/azure-cli/tree/dev/src/azure-cli/azure/cli/command_modules/resource) in above link.
+
+## Search its definition in `command.py`
+
+After entering the link, a command module folder generally contains the following files. You can find the command in `command.py`.
+```
+└─command module folder
+    └─ _help.py    # Store help information
+    └─ command.py    # Store command definition
+    └─ custom.py    # Store Custom method
+    └─ _params.py   # Store parameters information
+    └─....
+```
+Still the above sample `az resource group create`, You can find its definition on line 222 from [here](https://github.com/Azure/azure-cli/blob/dev/src/azure-cli/azure/cli/command_modules/resource/commands.py#L222).
+
+## Find the management client and corresponding SDK
+```python
+with self.command_group('group', resource_group_sdk, resource_type=ResourceType.MGMT_RESOURCE_RESOURCES) as g:
+    g.command('delete', 'begin_delete', supports_no_wait=True, confirmation=True)
+    g.show_command('show', 'get')
+    g.command('exists', 'check_existence')
+    g.custom_command('list', 'list_resource_groups', table_transformer=transform_resource_group_list)
+    g.custom_command('create', 'create_resource_group')
+    g.custom_command('export', 'export_group_as_template')
+    g.generic_update_command('update', custom_func_name='update_resource_group', custom_func_type=resource_custom)
+    g.wait_command('wait')
+```
+
+Taking the above code as an example, follow the  `resource_type` parameter in `command_group()` function find SDK name and client. like searching for the `MGMT_RESOURCE_RESOURCES` definition.
+```python
+# src/azure-cli-core/azure/cli/core/profiles/_shared.py
+MGMT_RESOURCE_RESOURCES = ('azure.mgmt.resource.resources', 'ResourceManagementClient')
+```
+You could find that its package name is `azure-mgmt-resource` and its client name is `ResourceManagementClient`.
+
+Then, you could it can be divided into three types in `command_group()` function: command()` function, `show_command()` function and `custom_command()` function.<br/>
+
+For the first two function, the first parameter comes from the CLI command, and the second parameter comes from the function name of the SDK.
+If you want to find the SDK function about `az resource group delete`, it is the `begin_delete`.<br/>
+![img.png](find_the_sdk.PNG)
+If it is a `custom_command()` function, you could find its definition in the `custom.py` In the peer path.
+Such as `create_resource_group()`, you could find the definition from [here](https://github.com/Azure/azure-cli/blob/dev/src/azure-cli/azure/cli/command_modules/resource/custom.py#L1310). (If it is not found, you could search for `create_resource_group` in this file.)
+```python
+def create_resource_group(cmd, rg_name, location, tags=None, managed_by=None):
+    """ Create a new resource group.
+    :param str resource_group_name:the desired resource group name
+    :param str location:the resource group location
+    :param str tags:tags in 'a=b c' format
+    """
+    rcf = _resource_client_factory(cmd.cli_ctx)
+
+    ResourceGroup = cmd.get_models('ResourceGroup')
+    parameters = ResourceGroup(
+        location=location,
+        tags=tags
+    )
+
+    if cmd.supported_api_version(min_api='2016-09-01'):
+        parameters.managed_by = managed_by
+
+    return rcf.resource_groups.create_or_update(rg_name, parameters)
+```
+Then, you could find the `create_or_update()` function in its return, it is the SDK function.
+
+## Find the function in Python SDK or Doc
+
+Similarly, find the `service` folder in the [SDK folder](https://github.com/Azure/azure-sdk-for-python/tree/main/sdk) of [SDK repo](https://github.com/Azure/azure-sdk-for-python).
+Such as [`resources` folder](https://github.com/Azure/azure-sdk-for-python/tree/main/sdk/resources).
+
+Then, you could find [here](https://github.com/Azure/azure-sdk-for-python/tree/main/sdk/resources/azure-mgmt-resource/azure/mgmt/resource/resources). This step may be a little difficult for beginners. It requires some experience.
+Don't be frightened by a lot of folders here. You can choose the latest date to enter, like [this](https://github.com/Azure/azure-sdk-for-python/tree/main/sdk/resources/azure-mgmt-resource/azure/mgmt/resource/resources/v2021_04_01).
+
+Enter the [_operation.py](https://github.com/Azure/azure-sdk-for-python/blob/main/sdk/resources/azure-mgmt-resource/azure/mgmt/resource/resources/v2021_04_01/operations/_operations.py) in the [operation folder](https://github.com/Azure/azure-sdk-for-python/tree/main/sdk/resources/azure-mgmt-resource/azure/mgmt/resource/resources/v2021_04_01/operations), and you can see the meta code.
+
+In this file, you could search the function name to find the function definition.(Be careful, the function need under the correct class.)
+Above the `begin_delete` function, you could find it from [here](https://github.com/Azure/azure-sdk-for-python/blob/main/sdk/resources/azure-mgmt-resource/azure/mgmt/resource/resources/v2021_04_01/operations/_operations.py#L8784).
+The same, the `create_or_update` function is [here](https://github.com/Azure/azure-sdk-for-python/blob/main/sdk/resources/azure-mgmt-resource/azure/mgmt/resource/resources/v2021_04_01/operations/_operations.py#L9761).
+
+Finally, you also could find the usage of function by [Azure doc](https://docs.microsoft.com/en-us/azure/developer/python/sdk/examples/azure-sdk-example-resource-group#3-write-code-to-provision-a-resource-group) or [Azure samples](https://github.com/Azure-Samples/azure-samples-python-management).
+
+Feel free to contact Azure SDK team at any time through any channels. We are passionate to build the world-class cloud product.