A woman in a black outfit lies face first on a yoga mat; several paintings are hanged on the wall, and the sun shines through a large window near her.
There is a person in a room.
From sentence one, we know that the woman is somewhere with a wall and a large window, this gives the impression of being in a room, which is explained by sentence 2.
A woman is a person.
If a woman is doing yoga in a place with paintings and windows, then that person is in a room.