isSubsetOf method
Evaluate whether this range is a subset of another.
that
The other range to compare to.
strict
Whether to consider strict subset (not equal).
Returns true if this range is a subset of the other range, false otherwise.
Implementation
bool isSubsetOf(Range<TYPE> that, {bool strict = false}) =>
!strict && _startGE(that) && _endLE(that) || strict && _startG(that) && _endL(that);