The ornamental design for a bag, as shown and described.
1. Bag
1.1: Perspective
1.2: Front
1.3: Back
1.4: Right
1.5: Left
1.6: Top
1.7: Bottom
1.8: Perspective
1.9: Perspective
1.10: Perspective of the bag open
1.11: Close-up
The bag comprises a shoulder strap and a body which, when viewed from the front, has the form of an isosceles trapezium with rounded corners; the body has a substantially rectangular bottom, two vertical side pleats, a main flap on the front, which covers the opening for accessing the inside compartment of the bag, and a shorter, secondary flap, at the rear, which covers a slot in the rear wall of the body, that provides access to an inside pocket of the bag.