input: Write a python function to find the top N most frequent words in a sentence.
  assert find_top_n_words("Python is an interpreted, high-level, general-purpose programming language.", 5) == [('Python', 1), ('is', 1), ('an', 1), ('interpreted,', 1), ('high-level,', 1)]
  assert find_top_n_words("the quick brown fox jumps over the lazy dog the the the", 3) == [('the', 4), ('quick', 1), ('brown', 1)]
  assert find_top_n_words("hello world hello hello hello world", 2) == [('hello', 4), ('world', 2)]
output: def find_top_n_words(sentence, n):
      from collections import Counter
      words = sentence.split()
      word_counts = Counter(words)
      top_n_words = word_counts.most_frequent(n)
      return top_n_words