You need to use a parameter page, for example. for the next 30 pages = 2
https://api.github.com/search/issues?q=stress+test+label:bug+language:python+state:closed&page=2
You can also use the option per_pageto change the default size to 30. It supports a maximum size of 100. For example:
https://api.github.com/search/issues?q=stress+test+label:bug+language:python+state:closed&per_page=100
More information can be found here.