motion to dismiss usually states: Even assuming everything the plaintiff alleged in her complain was true, the landlord would not be liable under the law.
Such as, I am hit by a driver, the driver was speeding because he was late for work, he's late for work because starbucks mixed up his coffee order.
I sue the driver and starbucks, and starbucks says, even if everything was true, assuming we did mixed up the driver's coffee, we are not liable for the driver's negligence.
Same goes for the landlord and tenant's dog.