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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def example_reading_spec(self):
 """Return a mix of env and video data fields and decoders."""

    video_fields, video_decoders = (
        video_utils.VideoProblem.example_reading_spec(self))
    env_fields, env_decoders = env_problem.EnvProblem.example_reading_spec(self)

    # Remove raw observations field since we want to capture them as videos.
    env_fields.pop(env_problem.OBSERVATION_FIELD)
    env_decoders.pop(env_problem.OBSERVATION_FIELD)

    # Add frame number spec and decoder.
    env_fields[_FRAME_NUMBER_FIELD] = tf.FixedLenFeature((1,), tf.int64)
    env_decoders[
        _FRAME_NUMBER_FIELD] = tf.contrib.slim.tfexample_decoder.Tensor(
            _FRAME_NUMBER_FIELD)

    # Add video fields and decoders
    env_fields.update(video_fields)
    env_decoders.update(video_decoders)
    return env_fields, env_decoders