input: Write a python function to check if a number is present in an array.
  assert checkNumber([2, 4, 6, 8], 8) == True
  assert checkNumber([2, 4, 6, 8], 5) == False
  assert checkNumber([1, 3, 5, 7], 3) == True
  assert checkNumber([], 1) == False
output: def checkNumber(arr, num):
      return num in arr