Returns true if the collection contains an element equal to [element].
Returns true if the collection contains an element equal to [element].
This operation will check each element in order for being equal to [element], unless it has a more efficient way to find an element equal to [element].
The equality used to determine whether [element] is equal to an element of the iterable defaults to the [Object.operator==] of the element.
Some types of iterable may have a different equality used for its elements.
For example, a [Set] may have a custom equality
(see [Set.identical]) that its contains
uses.
Likewise the Iterable
returned by a [Map.keys] call
should use the same equality that the Map
uses for keys.