docs: update oauth example (#886)

Author: tiwarishubham635

examples/public_oauth.py

@@ -4,27 +4,24 @@
 from twilio.credential.client_credential_provider import ClientCredentialProvider
 
 ACCOUNT_SID = os.environ.get("TWILIO_ACCOUNT_SID")
-API_KEY = os.environ.get("TWILIO_API_KEY")
-API_SECRET = os.environ.get("TWILIO_API_SECRET")
-FROM_NUMBER = os.environ.get("TWILIO_FROM_NUMBER")
-TO_NUMBER = os.environ.get("TWILIO_TO_NUMBER")
+MESSAGE_SID = os.environ.get("TWILIO_MESSAGE_SID")
 
 CLIENT_ID = os.environ.get("TWILIO_CLIENT_ID")
-CLIENT_SECRET = os.environ.get("CLIENT_SECRET")
+CLIENT_SECRET = os.environ.get("TWILIO_CLIENT_SECRET")
 
 
 def example():
     """
-    Some example usage of message resources.
+    An example usage of message resource.
     """
     client = Client(
         account_sid=ACCOUNT_SID,
         credential_provider=ClientCredentialProvider(CLIENT_ID, CLIENT_SECRET),
     )
 
-    msg = client.messages.create(
-        to=self.to_number, from_=self.from_number, body="hello world"
-    )
+    msg = client.messages(MESSAGE_SID).fetch()
+
+    print(msg)
 
 
 if __name__ == "__main__":