contains abstract method
- covariant String singleCharacterString
override
Whether singleCharacterString occurs in this
sequence of characters.
Returns true only if singleCharacterString is
a string containing a single character
and that character is one of the characters
in this character sequence, and false otherwise.
This behavior is inherited from Iterable<String>,
which is why it is not Characters-based.
Use containsAll for a method which acts like
String.contains for characters.
Implementation
@override
bool contains(covariant String singleCharacterString);