code: def _process_origin(self, req, resp, origin):
          
          if self._cors_config['allow_all_origins']:
              if self.supports_credentials:
                  self._set_allow_origin(resp, origin)
              else:
                  self._set_allow_origin(resp, '*')
              return True
  
          if origin in self._cors_config['allow_origins_list']:
              self._set_allow_origin(resp, origin)
              return True
  
          regex = self._cors_config['allow_origins_regex']
          if regex is not None:
              if regex.match(origin):
                  self._set_allow_origin(resp, origin)
                  return True
  
          return False
docs: Inspects the request and adds the Access-Control-Allow-Origin
          header if the requested origin is allowed.
  
          Returns:
              ``True`` if the header was added and the requested origin
              is allowed, ``False`` if the origin is not allowed and the
              header has not been added.