input: Write a function to check if an element exists in a list of integers.
  assert element_exists(3, [1, 2, 3, 4, 5]) == True
  assert element_exists(6, [1, 2, 3, 4, 5]) == False
  assert element_exists(0, [0, 1, 2, 3]) == True
output: def element_exists(element, lst):
      return element in lst