Dash is an offline documentation search engine. I've been using Dash a lot recently. It has very fast search and supports many libraries out there. Zeal is a free and ope source alternative to Dash that uses Dash doctests for offline documentation that supports all platforms. Other platform specific tools also exist such as Velocity for Windows and LovelyDocs for Android.
Dash supports many libraries however, libraries like Fabric and requests are not officially supported; their dash compatible doctests can be generated though. So, I thought I'd make a quick tutorial on how to generate doctests for third party libraries: