code: def set_value(self, key, value):
          # type: (str, Any) -> None
          
          self._ensure_have_load_only()
  
          fname, parser = self._get_parser_to_modify()
  
          if parser is not None:
              section, name = _disassemble_key(key)
  
              # Modify the parser and the configuration
              if not parser.has_section(section):
                  parser.add_section(section)
              parser.set(section, name, value)
  
          self._config[self.load_only][key] = value
          self._mark_as_modified(fname, parser)
docs: Modify a value in the configuration.