input: Write a python function to count the frequency of each string in a list.
  assert count_string_frequency(["apple", "banana", "apple", "orange", "banana", "apple"]) == {"apple": 3, "banana": 2, "orange": 1}
  assert count_string_frequency(["dog", "cat", "dog", "dog", "cat"]) == {"dog": 3, "cat": 2}
  assert count_string_frequency([]) == {}
output: def count_string_frequency(strings):
      frequency = {}
      for string in strings:
          if string in frequency:
              frequency[string] += 1
          else:
              frequency[string] = 1
      return frequency