input: Write a python function to append a new record to the list of people if it does not already exist.
  assert append_record([{"name": "Alice", "age": 8}, {"name": "Bob", "age": 11}], {"name": "Charlie", "age": 13}) == [{"name": "Alice", "age": 8}, {"name": "Bob", "age": 11}, {"name": "Charlie", "age": 13}]
  assert append_record([{"name": "Alice", "age": 8}, {"name": "Bob", "age": 11}], {"name": "Bob", "age": 11}) == [{"name": "Alice", "age": 8}, {"name": "Bob", "age": 11}]
  assert append_record([], {"name": "John", "age": 15}) == [{"name": "John", "age": 15}]
output: def append_record(records, new_record):
      if new_record not in records:
          records.append(new_record)
      return records