i1 : X = new HeaderType of BasicList o1 = X o1 : HeaderType
i2 : X {a,b,c} o2 = X{a, b, c} o2 : X
The object HeaderType is a type, with ancestor classes Type < MutableHashTable < HashTable < Thing.
The source of this document is in Macaulay2Doc/doc12.m2:19:0.