def METHOD_NAME(trf_header_contents: bytes) -> Header:
    """Decodes the header of a TRF file
    Parameters
    ----------
    trf_header_contents : bytes
        The header portion only of a TRF file. Use
        `determine_header_length` to extract the header portion only.
    Returns
    -------
    machine : str
        Machine ID. If it is set up to be serial number based something
        like '2619' could be expected.
    date : str
        UTC date. Eg '20/09/24 06:29:58 Z'.
    timezone : str
        Eg '+02:00'.
    field_label : str
        The first item that identifies the delivered field. Eg '1-1'.
        This item will be blank for service mode created beams.
    field_name : str
        The second item that identifies the delivered field. Eg 'AP G0'.
    """
    match = _header_match(trf_header_contents)
    groups = match.groups()
    # Decode data from first half of header. This comes from the first split groups
    date = groups[0].decode("utf-8")
    timezone = groups[1].decode("utf-8")
    field = groups[2].decode("utf-8")
    machine = groups[3].decode("utf-8")
    # Decode data from the second half of header. This comes from the first bytes of the last group
    mu = np.frombuffer(groups[4][0:8], dtype=np.float64).item()
    version = np.frombuffer(groups[4][8:12], dtype=np.int32).item()
    item_parts_number = np.frombuffer(groups[4][12:16], dtype=np.int32).item()
    # With the item_parts_length read from the header we can get a list of IPVs. This will be useful for a lookup later. These have to be read as in
    item_parts = np.frombuffer(
        groups[4][16 : 16 + 4 * item_parts_number], dtype=np.int16
    )
    item_parts_length = int(len(item_parts))
    split_field = field.split("/")
    if len(split_field) == 2:
        field_label, field_name = split_field
    else:
        field_label, field_name = "", field
    header = Header(
        machine,
        date,
        timezone,
        field_label,
        field_name,
        mu,
        version,
        item_parts_number,
        item_parts_length,
        item_parts,
    )
    return header