Returns a string representation of (some of) the elements of this.
Elements are represented by their own toString results.
The default representation always contains the first three elements. If there are less than a hundred elements in the iterable, it also contains the last two elements.
If the resulting string isn't above 80 characters, more elements are included from the start of the iterable.
The conversion may omit calling toString on some elements if they
are known to not occur in the output, and it may stop iterating after
a hundred elements.
Source
String toString() => IterableBase.iterableToFullString(this, "{", "}");