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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 parse_headers(header_list):
 """ Convert headers from our serialized dict with lists for keys to a HTTPMessage """

    header_string = b""
    for key, values in header_list.items():
        for v in values:
            header_string += \
                key.encode('utf-8') + b":" + v.encode('utf-8') + b"\r\n"
    return compat.get_httpmessage(header_string)