code: def validate_introspect_request(self, request):
          
          self._raise_on_missing_token(request)
          self._raise_on_invalid_client(request)
          self._raise_on_unsupported_token(request)
docs: Ensure the request is valid.
  
          The protected resource calls the introspection endpoint using
          an HTTP POST request with parameters sent as
          "application/x-www-form-urlencoded".
  
          token REQUIRED.  The string value of the token.
  
          token_type_hint OPTIONAL.
          A hint about the type of the token submitted for
          introspection.  The protected resource MAY pass this parameter to
          help the authorization server optimize the token lookup.  If the
          server is unable to locate the token using the given hint, it MUST
          extend its search across all of its supported token types.  An
          authorization server MAY ignore this parameter, particularly if it
          is able to detect the token type automatically.
              *  access_token: An Access Token as defined in [`RFC6749`],
                  `section 1.4`_
  
              *  refresh_token: A Refresh Token as defined in [`RFC6749`],
                  `section 1.5`_
  
          The introspection endpoint MAY accept other OPTIONAL
          parameters to provide further context to the query.  For
          instance, an authorization server may desire to know the IP
          address of the client accessing the protected resource to
          determine if the correct client is likely to be presenting the
          token.  The definition of this or any other parameters are
          outside the scope of this specification, to be defined by
          service documentation or extensions to this specification.
  
          .. _`section 1.4`: http://tools.ietf.org/html/rfc6749#section-1.4
          .. _`section 1.5`: http://tools.ietf.org/html/rfc6749#section-1.5
          .. _`RFC6749`: http://tools.ietf.org/html/rfc6749