sanitize docs

Author: gehrisandro

README.md

@@ -364,27 +364,20 @@ $stream = $client->chat()->createStreamed([
         ['role' => 'user', 'content' => 'Hello!'],
     ],
     'stream_options'=>[
-        'include_usage'=>true
+        'include_usage' => true,
     ]
 ]);
 
 foreach($stream as $response){
-    if($response->usage){
+    if($response->usage !== null){
         $response->usage->promptTokens; // 9,
         $response->usage->completionTokens; // 12,
         $response->usage->totalTokens; // 21
-    }else{
-        $response->choices[0]->toArray();
     }
-    
 }
-// 1. iteration => ['index' => 0, 'delta' => ['role' => 'assistant'], 'finish_reason' => null]
-// 2. iteration => ['index' => 0, 'delta' => ['content' => 'Hello'], 'finish_reason' => null]
-// 3. iteration => ['index' => 0, 'delta' => ['content' => '!'], 'finish_reason' => null]
-// ...
 ```
 
-When present, it contains a null value except for the last chunk which contains the token usage statistics for the entire request.
+ `usage` is always `null` except for the last chunk which contains the token usage statistics for the entire request.
 
 ### `Audio` Resource