[$] Doing symbolic math with SymPy

On November 29, version 1.7 of SymPy, a Python library forsymbolic mathematics, was released. The new version brings a large numberof enhancements and bug fixes, and some minor backwardincompatibilities. While these are enumerated in detail in the releasenotes, we will take advantage of this opportunity to look at some ofthe things that can be done with SymPy and explore its interface optionsthrough several detailed examples.