Why are duplicate tuples are not allowed in the relation code example

Example 1: Use the conditional operator in the checkEqual function to check if two numbers are equal or not. The function should return either "Equal" or "Not Equal".

function checkEqual(a, b) {
  return a === b ? "Equal" : "Not Equal";
}

Example 2: what are the mouseX/mouseY variebles in pycharm

x = mouseX
// mouse's x
y = mouseY
// mouse's y