add launch from python code doc (#3217)

docs/en_US/Tutorial/HowToLaunchFromPython.rst

+**How to Launch an experiment from Python**
+===========================================
+
+Overview
+--------
+Since ``nni v2.0``, we provide a new way to launch experiments. Before that, you need to configure the experiment in the yaml configuration file and then use the experiment ``nnictl`` command to launch the experiment. Now, you can also configure and run experiments directly in python file. If you are familiar with python programming, this will undoubtedly bring you more convenience.
+
+How to Use
+----------
+After successfully installing ``nni``, you can start the experiment with a python script in the following 3 steps.
+
+..
+
+    Step 1 - Initialize a tuner you want to use
+
+
+.. code-block:: python
+
+    from nni.algorithms.hpo.hyperopt_tuner import HyperoptTuner
+    tuner = HyperoptTuner('tpe')
+
+Very simple, you have successfully initialized a ``HyperoptTuner`` instance called ``tuner``.
+
+See all real `builtin tuners <../builtin_tuner.rst>`__ supported in NNI.
+
+..
+
+    Step 2 - Initialize an experiment instance and configure it
+
+.. code-block:: python
+
+    experiment = Experiment(tuner=tuner, training_service='local')
+
+Now, you have a ``Experiment`` instance with ``tuner`` you have initialized in the previous step, and this experiment will launch trials on your local machine due to ``training_service='local'``.
+
+See all `training services <../training_services.rst>`__ supported in NNI.
+
+.. code-block:: python
+
+    experiment.config.experiment_name = 'test'
+    experiment.config.trial_concurrency = 2
+    experiment.config.max_trial_number = 5
+    experiment.config.search_space = search_space
+    experiment.config.trial_command = 'python3 mnist.py'
+    experiment.config.trial_code_directory = Path(__file__).parent
+    experiment.config.training_service.use_active_gpu = True
+
+Use the form like ``experiment.config.foo = 'bar'`` to configure your experiment.
+
+See `parameter configuration <../reference/experiment_config.rst>`__ required by different training services.
+
+..
+
+    Step 3 - Just run
+
+.. code-block:: python
+
+    experiment.run(port=8081)
+
+Now, you have successfully launched an NNI experiment. And you can type ``localhost:8081`` in your browser to observe your experiment in real time.
+
+Example
+-------
+Below is an example for this new launching approach. You can also find this code in :githublink:`mnist-tfv2/launch.py <examples/trials/mnist-tfv2/launch.py>` .
+
+.. code-block:: python
+
+    from pathlib import Path
+    from nni.experiment import Experiment
+    from nni.algorithms.hpo.hyperopt_tuner import HyperoptTuner
+
+    tuner = HyperoptTuner('tpe')
+
+    search_space = {
+        "dropout_rate": { "_type": "uniform", "_value": [0.5, 0.9] },
+        "conv_size": { "_type": "choice", "_value": [2, 3, 5, 7] },
+        "hidden_size": { "_type": "choice", "_value": [124, 512, 1024] },
+        "batch_size": { "_type": "choice", "_value": [16, 32] },
+        "learning_rate": { "_type": "choice", "_value": [0.0001, 0.001, 0.01, 0.1] }
+    }
+
+    experiment = Experiment(tuner, 'local')
+    experiment.config.experiment_name = 'test'
+    experiment.config.trial_concurrency = 2
+    experiment.config.max_trial_number = 5
+    experiment.config.search_space = search_space
+    experiment.config.trial_command = 'python3 mnist.py'
+    experiment.config.trial_code_directory = Path(__file__).parent
+    experiment.config.training_service.use_active_gpu = True
+
+    experiment.run(8081)
+
+API
+---
+
+..  autoclass:: nni.experiment.Experiment
+    :members:

docs/en_US/nnicli_ref.rst

@@ -25,17 +25,3 @@ NNI client is a python API of ``nnictl``\ , which implements the most commonly u
 
    # stop the experiment, then disconnect the instance from the experiment.
    exp.stop_experiment()
-
-References
-----------
-
-..  autoclass:: nni.experiment.Experiment
-    :members:
-..  autoclass:: nni.experiment.TrialJob
-    :members:
-..  autoclass:: nni.experiment.TrialHyperParameters
-    :members:
-..  autoclass:: nni.experiment.TrialMetricData
-    :members:
-..  autoclass:: nni.experiment.TrialResult
-    :members:

docs/en_US/reference.rst

@@ -11,3 +11,4 @@ References
     NNI Annotation <Tutorial/AnnotationSpec>
     SDK API References <sdk_reference>
     Supported Framework Library <SupportedFramework_Library>
+    Launch from python <Tutorial/HowToLaunchFromPython>

nni/experiment/experiment.py

@@ -70,7 +70,7 @@ class Experiment:
             A tuner instance.
         training_service
             Name of training service.
-            Supported value: "local", "remote", "openpai".
+            Supported value: "local", "remote", "openpai", "aml", "kubeflow", "frameworkcontroller", "adl" and hybrid training service.
         """
         ...