code: def build_defaults(self):
          
          defaults = {}
          for arg in self.args:
              if not isinstance(arg, _BaseOpt):
                  raise errors.InvalidSchemeError('Unable to build default for non-Option type')
  
              # if there is a default set, add it to the defaults dict
              if not isinstance(arg.default, NoDefault):
                  defaults[arg.name] = arg.default
  
              # if we have a dict option, build the defaults for its scheme.
              # if any defaults exist, use them.
              if isinstance(arg, DictOption):
                  if arg.scheme:
                      b = arg.scheme.build_defaults()
                      if b:
                          defaults[arg.name] = b
          return defaults
docs: Build a dictionary of default values from the `Scheme`.
  
          Returns:
              dict: The default configurations as set by the `Scheme`.
  
          Raises:
              errors.InvalidSchemeError: The `Scheme` does not contain
                  valid options.