Loading a corpus reader can be an expensive operation due to the number of files, file sizes, and various initialization tasks. And while you'll often want to specify a corpus reader in a common module, you don't always need to access it right away. To speed up module import time when a corpus reader is defined, NLTK provides a LazyCorpusLoader class that can transform itself into your actual corpus reader as soon as you need it. This way, you can define a corpus reader in a common module without it slowing down module loading.