input: Write a python function to count the frequency of each word in a given sentence.
  assert count_word_frequency('the quick brown fox jumps over the lazy dog')==[('lazy', 1), ('dog', 1), ('brown', 1), ('jumps', 1), ('quick', 1), ('the', 2), ('over', 1), ('fox', 1)]
  assert count_word_frequency('hello hello world')==[('hello', 2), ('world', 1)]
  assert count_word_frequency('a a a a b b')==[('a', 4), ('b', 2)]
output: def count_word_frequency(sentence):
      words = sentence.split()
      frequency = {}
      for word in words:
          if word in frequency:
              frequency[word] += 1
          else:
              frequency[word] = 1
      return sorted(frequency.items(), key=lambda item: item[0])