input: Write a python function to identify characters that are flanked by vowels in the provided string.
  assert count_vowels('bestinstareels') == 7
  assert count_vowels('partofthejourneyistheend') == 12
  assert count_vowels('amazonprime') == 5
output: def count_vowels(s):
      vowels = "aeiou"
      count = 0
      for i in range(1, len(s) - 1):
          if s[i - 1] in vowels and s[i + 1] in vowels:
              count += 1
      return count