input: Write a python function to check if an element is in an array.
  assert element_in_array([1, 2, 3, 4, 5], 3) == True
  assert element_in_array([1, 2, 3, 4, 5], 6) == False
  assert element_in_array(['a', 'b', 'c', 'd'], 'c') == True
  assert element_in_array(['a', 'b', 'c', 'd'], 'e') == False
output: def element_in_array(arr, elem):
      return elem in arr