This is an interface and should not be constructed.
Allows parsers that should only run a single time, and that should not repeatedly re-parse their own output.
This method is optional. Parsers that don't implement it are not considered to be single-use parsers by default.
Parses a value and either returns the parsed value upon success, otherwise returns
Name Type Description
String the unparsed value. May be null.
Object the attributes appropriate to the
Returns:the parsed value, or
nullif the value was not recognised.