Orca TF Estimator Documentation (intel-analytics#2710)

* init orca tf estimator docs

* move orca tf estimator doc

* update estimtor api

python/orca/src/bigdl/orca/learn/tf/estimator.py

@@ -35,11 +35,22 @@ def evaluate(self, data, **kwargs):
         pass
 
     def load_orca_checkpoint(self, path, version):
+        """
+        Load specified Orca checkpoint.
+        :param path: checkpoint directory which contains model.* and
+        optimMethod-TFParkTraining.* files.
+        :param version: checkpoint version, which is the suffix of model.* file,
+        i.e., for modle.4 file, the version is 4.
+        """
         self.load_checkpoint = True
         self.checkpoint_path = path
         self.checkpoint_version = version
 
     def load_latest_orca_checkpoint(self, path):
+        """
+        Load latest Orca checkpoint under specified directory.
+        :param path: directory containing Orca checkpoint files.
+        """
         ckpt_path, version = find_latest_checkpoint(path)
         if ckpt_path is None:
             raise Exception("Cannot find checkpoint")
@@ -64,8 +75,7 @@ def set_tensorboard(self, log_dir, app_name):
     def get_train_summary(self, tag=None):
         """
         Get the scalar from model train summary
-        Return 2-D array like object which could be converted
-        by nd.array()
+        Return list of summary data of [iteration_number, scalar_value, timestamp]
         # Arguments
         tag: The string variable represents the scalar wanted
         """
@@ -77,8 +87,7 @@ def get_train_summary(self, tag=None):
     def get_validation_summary(self, tag=None):
         """
         Get the scalar from model validation summary
-        Return 2-D array like object which could be converted
-        by np.array()
+        Return list of summary data of [iteration_number, scalar_value, timestamp]
 
         Note: The metric and tag may not be consistent
         Please look up following form to pass tag parameter