request = tornado.httpclient.HTTPRequest(url='http://www.example.com', method='GET')
body = {'key': 'value'} headers = {'Content-Type': 'application/json'} request = tornado.httpclient.HTTPRequest(url='http://www.example.com', method='POST', headers=headers, body=json.dumps(body))
params = {'key': 'value'} request = tornado.httpclient.HTTPRequest(url='http://www.example.com', method='GET', params=params)In this example, we create an instance of `HTTPRequest` with the URL, method and query parameters as parameters. Overall, the `HTTPRequest` class provides a flexible way to construct HTTP requests. It is a part of the `tornado.httpclient` package library in Python.