"installer" is a low-level library for installing a Python package from a
 wheel distribution; the wheel is the basic unit of Python module
 distribution to end users. It provides basic functionality and abstractions
 for handling wheels and installing packages from wheels, including:
 .
  * Logic for "unpacking" a wheel (i.e. installation).
  * Abstractions for various parts of the unpacking process.
  * Extensible simple implementations of the abstractions.
  * Platform-independent Python script wrapper generation.