input: Write a python function to count the occurrences of each word in a given string.
  assert word_count("Hello world, This is me") == {'Hello': 1, 'world,': 1, 'This': 1, 'is': 1, 'me': 1}
  assert word_count("apple banana apple orange banana apple") == {'apple': 3, 'banana': 2, 'orange': 1}
  assert word_count("one fish two fish red fish blue fish") == {'one': 1, 'fish': 4, 'two': 1, 'red': 1, 'blue': 1}
output: def word_count(s):
      words = s.split()
      word_freq = {}
      for word in words:
          if word in word_freq:
              word_freq[word] += 1
          else:
              word_freq[word] = 1
      return word_freq