input: Write a function to count the number of words in a given string. Return the count of words in the output. 
  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('Count these words')==3
output: def count_words(s):
      if s.strip() == "":
          return 0
      return len(s.split())