This is an interface and should not be constructed.
Single Use Parser()
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
the unparsed value. May be null.
the attributes appropriate to the
the parsed value, or
null if the value was not recognised.