input: Write a function to count the number of words in a given string. The function should return the count of words.
  def count_words(string):
      return len(string.split())
  assert count_words('Hello world, this is a sentence.')==5
  assert count_words('This is another example.')==4
  assert count_words('')==0
  assert count_words('One')==1
  assert count_words('Two words')==2
output: def count_words(string):
      return len(string.split())