The object INPUT (missing documentation) is a markup type, with ancestor classes HypertextVoid (missing documentation) < Hypertext < BasicList < Thing.
The source of this document is in /builddir/build/BUILD/Macaulay2-1.25.05-build/M2-release-1.25.05/M2/BUILD/x86_64-redhat-linux-gnu/Macaulay2/packages/Text-temporary/currentString:1:427.