input: Write a function to count occurrences of a specific character in a given string.
  assert countOccurrence("The quick brown fox", "q") == 1
  assert countOccurrence("hello world", "o") == 2
  assert countOccurrence("mississippi", "s") == 4
output: def countOccurrence(s: str, char: str) -> int:
      return s.count(char)