removeRange method Null safety
override
Removes the objects in the range start inclusive to end exclusive.
The provided range, given by start and end, must be valid.
A range from start to end is valid if 0 <= start <= end <= len, where
len is this list's length. The range starts at start and has length
end - start. An empty range (with end == start) is valid.
Throws an UnsupportedError if this is a fixed-length list. In that case the list is not modified.
Implementation
void removeRange(int start, int end) {
RangeError.checkValidRange(start, end, this.length);
if (end > start) {
_closeGap(start, end);
}
}