SanityCheck is the name of an optional argument. Its value is a Boolean value, which determines whether or not to check if a supposed solution of the deformation equation actually satisfies it. Default value is true.
The object SanityCheck is a symbol.
The source of this document is in /__w/M2/M2/macaulay2-1.26.05+ds/M2/Macaulay2/packages/VersalDeformations.m2:890:0.