txt in the api gw root.yml

openapi: "3.0.1"
info:
  title: "demo-test-verification"
  version: "2019-12-27T23:52:02Z"
servers:
- url: "https://xxx.execute-api.us-east-1.amazonaws.com/{basePath}"
  variables:
    basePath:
      default: "/prod"
paths:
  /:
    get:
      responses:
        200:
          description: "200 response"
          content:
            text/plain:
              schema:
                $ref: "#/components/schemas/Text"
      x-amazon-apigateway-integration:
        responses:
          default:
            statusCode: "200"
            responseTemplates:
              text/plain: "hello world\n"
        passthroughBehavior: "when_no_match"
        requestTemplates:
          application/json: "{\"statusCode\": 200}"
        type: "mock"
components:
  schemas:
    Text:
      title: "Empty Text Schema"
      type: "object"