input: Write a python function to count the number of occurrences of a specific character in a string.
  assert count_char_occurrences('Google', 'o') == 2
  assert count_char_occurrences('hello world', 'l') == 3
  assert count_char_occurrences('test case', 't') == 2
output: def count_char_occurrences(s: str, char: str) -> int:
      return s.count(char)