add support for 'high'/'medium'/'low' think values

currently only supported on gpt-oss, but as more models come out with
support like this we'll likely relax the particular values that can be
provided

examples/README.md

@@ -73,3 +73,6 @@ Requirement: `pip install tqdm`
 
 ### Thinking (generate) - Enable thinking mode for a model
 - [thinking-generate.py](thinking-generate.py)
+
+### Thinking (levels) - Choose the thinking level
+- [thinking-levels.py](thinking-generate.py)

examples/thinking-levels.py

@@ -0,0 +1,26 @@
+from ollama import chat
+
+
+def heading(text):
+  print(text)
+  print('=' * len(text))
+
+
+messages = [
+  {'role': 'user', 'content': 'What is 10 + 23?'},
+]
+
+# gpt-oss supports 'low', 'medium', 'high'
+levels = ['low', 'medium', 'high']
+for i, level in enumerate(levels):
+  response = chat('gpt-oss:20b', messages=messages, think=level)
+
+  heading(f'Thinking ({level})')
+  print(response.message.thinking)
+  print('\n')
+  heading('Response')
+  print(response.message.content)
+  print('\n')
+  if i < len(levels) - 1:
+    print('-' * 20)
+    print('\n')