input: Write a python function to add, retrieve, and delete customer information from a SQLite database.
  assert customer_data.write(Customer('Alice', 30)).name == 'Alice'
  assert customer_data.get('Alice').age == 30
  customer_data.delete('Alice')
  assert customer_data.get('Alice') == None
output: import sqlite3
  
  class Customer:
      def __init__(self, name, age):
          self.name = name
          self.age = age
  
  class CustomerData:
      def __init__(self, db_name='customers.db'):
          self.conn = sqlite3.connect(db_name)
          self.create_table()
  
      def create_table(self):
          with self.conn:
              self.conn.execute('''
                  CREATE TABLE IF NOT EXISTS customers (
                      name TEXT PRIMARY KEY,
                      age INTEGER
                  )
              ''')
  
      def write(self, customer):
          with self.conn:
              self.conn.execute('''
                  INSERT OR REPLACE INTO customers (name, age) VALUES (?, ?)
              ''', (customer.name, customer.age))
          return customer
  
      def get(self, name):
          cursor = self.conn.cursor()
          cursor.execute('SELECT name, age FROM customers WHERE name=?', (name,))
          row = cursor.fetchone()
          if row:
              return Customer(row[0], row[1])
          return None
  
      def delete(self, name):
          with self.conn:
              self.conn.execute('DELETE FROM customers WHERE name=?', (name,))
  
  customer_data = CustomerData()
  
  # Example usage
  customer_data.write(Customer('Alice', 30))
  assert customer_data.get('Alice').age == 30
  customer_data.delete('Alice')
  assert customer_data.get('Alice') == None