Fixture could not fill depended fields in list

[coderfly]

fixture_data_embedded = {
    'post1': {
        'title': 'Sherlock Gets A Musical Parody',
        'text': 'Sherlock fans still have a way to go before Season 4 of the BBC drama finally arrives.',
        'authors': [
          {
            'id': '{users.user1}',
            'first_name': 'Joyce',
            'last_name': 'Ray'
          },
          {
            'id': '{users.user2}',
            'first_name': 'Amy',
            'last_name': 'Myers'
          }
        ],
    }
}