code: public boolean parse(Context context, ProcPatternElement terminator) {
          if (isNextIn(context)) {
              if(!ghost) {
                  context.getSource().incOffset(valueLength);
              }
              return true;
          } else {
              return false;
          }
      }
docs: Parse constant
  
  @param context    current context
  @param terminator not used
  @return true - if next sequence in source equals to this constant value,
  false - other