input: Write a python function to count the frequency of elements in a list of dictionaries.
  assert count_frequency([{'a': 1, 'b': 2}, {'a': 2, 'c': 1}]) == {1: 2, 2: 2}
  assert count_frequency([{'a': 3}, {'b': 3}, {'c': 3, 'd': 4}]) == {3: 3, 4: 1}
  assert count_frequency([{'a': 5}, {'b': 6}, {'c': 5, 'd': 6}]) == {5: 2, 6: 2}
output: def count_frequency(list_of_dicts):
      frequency = {}
      for d in list_of_dicts:
          for value in d.values():
              if value in frequency:
                  frequency[value] += 1
              else:
                  frequency[value] = 1
      return frequency