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Pysa is a security-focused tool build on the top of Pyre, Facebook's type checker for python. It checks code and analyzes how data flows through it. It helps to scale application security efforts for python which is the most important codebase which powers Instagram’s servers. The most common kinds of sources are places where user-controlled data enters the application like Django's HttpRequest.GET dictionary. It performs some rounds of analysis to build summaries to determine which functions have parameters that eventually reach a sink.