ref: update make_checkpoint example

Author: jorgeorpinel

content/docs/api-reference/make_checkpoint.md

@@ -27,18 +27,14 @@ by the code in stages executes by `dvc exp run` (see `cmd` field of `dvc.yaml`).
 > Note that for non-Python code, the alternative is to write a
 > `.dvc/tmp/DVC_CHECKPOINT` signal file.
 
-## Exceptions
-
-None
-
-## Example: Mark a checkpoint every 100 iterations
+## Example: Every 100th iteration
 
 Let's consider the following `dvc.yaml` file:
 
 ```yaml
 stages:
   foo:
-    cmd: python src/mystage.py
+    cmd: python iterate.py
     params:
       - start
     outs:
@@ -49,35 +45,31 @@ stages:
 > See `dvc params` for information on stage parameters.
 
 Here's the example code that the stage above will execute. It continuously
-increments an integer value in the `int.txt` file, starting at the `start`
-param. It makes a checkpoint with `dvc exp` every time the value adds 100:
+increments an integer value in `int.txt`, starting at the `start` param. It
+makes a checkpoint with `dvc exp` every time the value adds 100:
 
 ```py
 import os
-from ruamel.yaml import YAML
 from dvc.api import make_checkpoint
 
 output_file = "int.txt"
-
-with open("params.yaml") as fobj:
-    params = yaml.load(fobj)
-start = params.get("start", 0)
+start = _load_param('start') # Load start from params.yaml
 
 while True:
     try:
         if os.path.exists(output_file):
-            with open(output_file, "r") as fobj:
+            with open(output_file, "r") as fd:
                 try:
-                    data = fobj.read()
-                    iter_ = int(data) + 1
+                    iter_ = int(fd.read()) + 1
                 except ValueError:
                     iter_ = start
         else:
             iter_ = start
 
-        with open(output_file, "w") as fobj:
+        with open(output_file, "w") as fd:
             fobj.write(f"{iter_}")
 
         if iter_ % 100 == 0:
             make_checkpoint()
+    # ...
 ```