input: Write a python function to retrieve the value of a given key from the dictionary person_details.
  assert get_detail('Name') == 'John'
  assert get_detail('Age') == 27
  assert get_detail('Gender') == 'Male'
output: def get_detail(key):
      person_details = {
          'Name': 'John',
          'Age': 27,
          'Gender': 'Male'
      }
      return person_details.get(key)