input: Write a python function to get documentation of a selected API from a list of APIs.
  assert type(list_apis()) == list
  assert 'example_api' in list_apis()
  assert type(select_api('example_api')) == dict
  assert type(get_doc('example_api')) == dict
output: def list_apis():
      return ['example_api']
  
  def select_api(api_name):
      apis = {
          'example_api': {
              'name': 'Example API',
              'version': '1.0',
              'documentation': 'This is an example API for demonstration purposes.'
          }
      }
      return apis.get(api_name)
  
  def get_doc(api_name):
      api_info = select_api(api_name)
      if api_info:
          return {
              'name': api_info['name'],
              'version': api_info['version'],
              'documentation': api_info['documentation']
          }
      return {}