input: Write a function to generate sample data for a web application using Python's faker library. The function should return a list of dictionaries, with each dictionary containing three key-value pairs: 'name', 'email', and 'age'. Each dictionary represents a single user's data, and the function should generate data for 10 users.
  
  def generate_sample_data():
      from faker import Faker
      fake = Faker()
      data = []
      for _ in range(10):
          user = {
              'name': fake.name(),
              'email': fake.email(),
              'age': fake.random_int(min=18, max=60)
          }
          data.append(user)
      return data
  
  assert isinstance(generate_sample_data(), list)
  assert len(generate_sample_data()) == 10
  assert all(isinstance(user, dict) and len(user) == 3 for user in generate_sample_data())
output: def generate_sample_data():
      from faker import Faker
      fake = Faker()
      data = []
      for _ in range(10):
          user = {
              'name': fake.name(),
              'email': fake.email(),
              'age': fake.random_int(min=18, max=60)
          }
          data.append(user)
      return data