input: Write a python function to find the most frequent number in a given array.
  assert get_most_frequent([10, 8, 8, 9, 10, 11, 12, 12, 11])==11
  assert get_most_frequent([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])==1
  assert get_most_frequent([10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 10, 20, 30, 10])==10
output: def get_most_frequent(arr):
      from collections import Counter
      counter = Counter(arr)
      most_common = counter.most_common(1)
      return most_common[0][0] if most_common else None