<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def pack_chunk(source_data: bytes) -> str: """ Packs the specified binary source data by compressing it with the Zlib library and then converting the bytes to a base64 encoded string for non-binary transmission. :param source_data: The data to be converted to a compressed, base64 string """

    if not source_data:
        return ''

    chunk_compressed = zlib.compress(source_data)
    return binascii.b2a_base64(chunk_compressed).decode('utf-8')