Adjust the Instant Pot to the Saute setting and add a tablespoon of canola oil. When the oil is hot, saute chopped onions for about five minutes until they're translucent, then remove them with a slotted spoon into a bowl and set aside. 

Add the last tablespoon of canola oil and maintain the Saute setting. Brown the ground beef, add the taco seasoning, cumin, Mexican-style chili powder, salt, and freshly cracked black peppercorns to taste, and mix well. 

When the ground beef is cooked through and browned, strain off all of the excess dripping.

Into the Instant Pot, add the pinto beans, black beans, sweet corn kernels, whole tomatoes, crushed tomatoes, jalapeño peppers, and one-quarter (1/4) cup chopped cilantro.

Stir the ingredients until thoroughly combined. 

Fold in the sour cream and continue to mix until the sour cream is fully incorporated.  

Place the lid of the Instant Pot, and lock it into place. Select the Bean/Chili setting and cook for 10 minutes.

Vent the Instant Pot and remove the lid.

Ladle the soup into serving bowls and top with green onion, cilantro, and Mexican cheeses. 

Serve with corn tortilla chips.