public function boolean()
    {
        $message = ['%s is {{not|}} a boolean', $this->value];
        $this->assert(is_bool($this->value), $message);

        return $this;
    }
public function boolean()
    {
        $message = ['%s is {{not|}} a boolean', $this->value];
        $this->assert(is_bool($this->value), $message);

        return $this;
    }
public function boolean ( ) { $ message = [ '%s is {{not|}} a boolean' , $ this -> value ] ; $ this -> assert ( is_bool ( $ this -> value ) , $ message ) ; return $ this ; }
Assert that the value is a boolean type.

@throws AssertionFailureException

@return self
Assert that the value is a boolean type .