<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_convolutional_encoder(config: ConvolutionalEncoderConfig, prefix: str) -> 'Encoder': """ Creates a convolutional encoder. :param config: Configuration for convolutional encoder. :param prefix: Prefix for variable names. :return: Encoder instance. """

    encoder_seq = EncoderSequence([], dtype=config.dtype)
    cls, encoder_params = _get_positional_embedding_params(config.positional_embedding_type,
                                                           config.num_embed,
                                                           max_seq_len=config.max_seq_len_source,
                                                           fixed_pos_embed_scale_up_input=False,
                                                           fixed_pos_embed_scale_down_positions=True,
                                                           prefix=prefix + C.SOURCE_POSITIONAL_EMBEDDING_PREFIX)
    encoder_seq.append(cls, **encoder_params)
    encoder_seq.append(ConvolutionalEncoder, config=config)
    return encoder_seq