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