<itemvalue="The [State] for the widget in the tree that currently has this global key. The current state is null if (1) there is no widget in the tree that matches this global key, (2) that widget is not a [StatefulWidget], or the associated [State] object is not a subtype of `T`."/>
<itemvalue="source model"/>
<itemvalue="The characters of a string. A character is a Unicode Grapheme cluster represented by a substring of the original string. The `Characters` class is an [Iterable] of those strings. However, unlike most iterables, many of the operations are eager. Since the underlying string is known in its entirety, and is known not to change, operations which select a subset of the elements can be computed eagerly, and in that case the operation returns a new `Characters` object. The [iterator] provided by [Characters] is a [CharacterRange] which allows iterating the independent characters in both directions, but which also provides ways to select other ranges of characters in different ways."/>
