code: def unusedoptions(self, sections):
          
          unused = set([])
          for section in _list(sections):
              if not self.has_section(section):
                  continue
              options = self.options(section)
              raw_values = [self.get(section, option, raw=True) for option in options]
              for option in options:
                  formatter = "%(" + option + ")s"
                  for raw_value in raw_values:
                      if formatter in raw_value:
                          break
                  else:
                      unused.add(option) 
              return list(unused)
docs: Lists options that have not been used to format other values in 
          their sections. 
          
          Good for finding out if the user has misspelled any of the options.