input: Write a function to check if an element exists within a given list of integers. Return True if the element exists within the list, otherwise return False.
  assert element_exists(5, [1, 3, 5, 7])==True
  assert element_exists(2, [1, 3, 5, 7])==False
  assert element_exists(7, [1, 3, 5, 7])==True
  assert element_exists(0, [1, 3, 5, 7])==False
  assert element_exists(0, [])==False
output: def element_exists(element, lst):
      return element in lst