[DLMED] enhance doc (#712)

Signed-off-by: Nic Ma <nma@nvidia.com>

Author: Nic-Ma

modules/bundle/get_started.ipynb

@@ -149,7 +149,9 @@
     "\n",
     "Please note that a MONAI bundle doesn't require any hard-coded logic in the config, so users can define the config content in any structure.\n",
     "\n",
-    "For the first step, import `os` and `glob` to use in the expressions (start with `$`), then define input / output environments and enable `cudnn.benchmark` for better performance."
+    "For the first step, import `os` and `glob` to use in the `python expressions` (start with `$`), then define input / output environments and enable `cudnn.benchmark` for better performance.\n",
+    "\n",
+    "Note that the `imports` are only used to execute the `python expressions`, and already imported `monai`, `numpy`, `np`, `torch` internally as these are mininum dependencies of MONAI."
    ]
   },
   {
@@ -180,7 +182,9 @@
     "\n",
     "Define `UNet` of MONAI as the training network, and use the `Adam` optimizer of PyTorch, `DiceCELoss` of MONAI.\n",
     "\n",
-    "An instantiable config component uses `_target_` keyword to define the class / function name or module path, other keys are args for the component."
+    "An instantiable config component uses `_target_` keyword to define the class / function name or module path, other keys are args for the component.\n",
+    "\n",
+    "Note that for all the MONAI classes and functions, we can use its name in `_target_` directly, for any other packages, please provide the `full module path` in `_target_`."
    ]
   },
   {
@@ -652,7 +656,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.8.12"
+   "version": "3.8.13"
   }
  },
  "nbformat": 4,