bool contains(
Object 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.

Source

/**
 * 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.
 */
bool contains(Object element);