This code creates an environment, builds the 'myapp' executable, and then creates an alias called 'build' that points to the 'myapp' target. Now, when you run 'scons build', it will automatically build the 'myapp' target. Another example is creating an alias for running unit tests:python env = Environment() tests = env.Program('unit_tests', ['test1.cpp', 'test2.cpp', 'test3.cpp']) alias = Alias('test', tests, [env.Command('data.txt', 'testdata/gen_data.py', '$SOURCE')]) ``` This code builds an executable called 'unit_tests' and adds a command to generate test data. It then creates an alias called 'test' that depends on the 'unit_tests' target and the 'data.txt' target. To determine the package library for SCons, you can check the documentation or the source code. SCons uses a number of Python libraries, including argparse, collections, distutils, glob, itertools, os, re, sys, tempfile, and unittest, among others.