How to create physics for the whole map in SpriteKit?

Question

Swift

If this is how we take our scene layer and create physics for it

self.ground = self.childNode(withName: "//Ground") as! SKTileMapNode
self.ground.physicsBody = SKPhysicsBody(texture: self.texture, size: self.ground.tileSize)

then it turns out that the physics is created in the image of our texture, but not in the image of the entire map

Question: How to create a physical body for the entire layer at once ???