public Grammar register(@NonNull ParserTokenType type, @NonNull PrefixHandler handler) {
      prefixHandlers.put(type, handler);
      return this;
   }
public Grammar register ( @ NonNull ParserTokenType type , @ NonNull PrefixHandler handler ) { prefixHandlers . put ( type , handler ) ; return this ; }
Registers a prefix handler

@param type    The token type that causes the prefix handler to parse
@param handler The prefix handler
@return This grammar (for fluent pattern)