input: Write a function to find the maximum age from a list of dictionaries.
  assert find_max_age([{'name': 'John', 'age': 19}, {'name': 'Mark', 'age': 22}, {'name': 'Mary', 'age': 17}])==22
  assert find_max_age([{'name': 'Alice', 'age': 30}, {'name': 'Bob', 'age': 25}, {'name': 'Charlie', 'age': 35}])==35
  assert find_max_age([{'name': 'Tom', 'age': 40}, {'name': 'Jerry', 'age': 38}, {'name': 'Spike', 'age': 42}])==42
output: def find_max_age(lst):
      return max(person['age'] for person in lst)