DependentCell<T> constructor
Create a cell, of which the value depends on a list of argument cells.
arguments
is the set of all the argument cells on which the value
of this cell depends.
If key
is non-null, the returned DependentCell object will compare
== to all DependentCell objects with the same key
under ==.
Implementation
DependentCell(this.arguments, {
key,
}) {
this.key = key ?? AutoKey.autoKey(this);
}