code: public function setIdentity($identity)
      {
          if ($identity instanceof IdentityInterface) {
              $this->_identity = $identity;
          } elseif ($identity === null) {
              $this->_identity = null;
          } else {
              throw new InvalidValueException('The identity object must implement IdentityInterface.');
          }
          $this->_access = [];
      }
docs: Sets the user identity object.
  
  Note that this method does not deal with session or cookie. You should usually use [[switchIdentity()]]
  to change the identity of the current user.
  
  @param IdentityInterface|null $identity the identity object associated with the currently logged user.
  If null, it means the current user will be a guest without any associated identity.
  @throws InvalidValueException if `$identity` object does not implement [[IdentityInterface]].