docs: def load_public_key(vm_):
      '''
      Load the public key file if exists.
      '''
      public_key_filename = config.get_cloud_config_value(
          'ssh_public_key', vm_, __opts__, search_global=False, default=None
      )
      if public_key_filename is not None:
          public_key_filename = os.path.expanduser(public_key_filename)
          if not os.path.isfile(public_key_filename):
              raise SaltCloudConfigError(
                  'The defined ssh_public_key \'{0}\' does not exist'.format(
                      public_key_filename
                  )
              )
  
          with salt.utils.files.fopen(public_key_filename, 'r') as public_key:
              key = salt.utils.stringutils.to_unicode(public_key.read().replace('\n', ''))
  
              return key