How to Check if Character is Grounded on Tilemap

Hi,

New to Unity here! What does the script look like for checking if the character is grounded on a Tilemap Composite Collider 2D? I had it working before by looping to check through a bunch of BoxColliders2D, but I think I'm missing something with how the Tilemap Colliders work. Is Tilemap considered one collider, or still a series of colliders I should loop through? Please and thank you!