@uml Get the {@link CharStream} from which this token source is currently providing tokens.
@return The {@link CharStream} associated with the current position in the input, or {@code null} if no input stream is available for the token source.
See Implementation
@uml Get the {@link CharStream} from which this token source is currently providing tokens.
@return The {@link CharStream} associated with the current position in the input, or {@code null} if no input stream is available for the token source.