How to enable / disable thinking feature in Gemini 2.5 Pro using Gemini.R (Vertex AI)

Hi @jhk0530 , We are using gemini.R for some our OCR text extraction use case through our service organization (Vertex AI Platform). We have been using Gemini 2.5 Pro for Image extraction. But lately, we notice it is using its thinking capability to extract the text values from the image. Could you please let us know how to turn off / turn on the thinking feature in Gemini 2.5 Pro models https://ai.google.dev/gemini-api/docs/thinking Thanks Arun Rajesh B.