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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 _find_channel(connection, name, ctype, dtype, sample_rate, unique=False):
 """Internal method to find a single channel Parameters connection : `nds2.connection`, optional open NDS2 connection to use for query name : `str` the name of the channel to find ctype : `int` the NDS2 channel type to match dtype : `int` the NDS2 data type to match sample_rate : `tuple` a pre-formatted rate tuple (see `find_channels`) unique : `bool`, optional, default: `False` require one (and only one) match per channel Returns ------- channels : `list` of `nds2.channel` list of NDS2 channel objects, if `unique=True` is given the list is guaranteed to have only one element. See also -------- nds2.connection.find_channels for documentation on the underlying query method """

    # parse channel type from name,
    # e.g. 'L1:GDS-CALIB_STRAIN,reduced' -> 'L1:GDS-CALIB_STRAIN', 'reduced'
    name, ctype = _strip_ctype(name, ctype, connection.get_protocol())

    # query NDS2
    found = connection.find_channels(name, ctype, dtype, *sample_rate)

    # if don't care about defaults, just return now
    if not unique:
        return found

    # if two results, remove 'online' copy (if present)
    #    (if no online channels present, this does nothing)
    if len(found) == 2:
        found = [c for c in found if
                 c.channel_type != Nds2ChannelType.ONLINE.value]

    # if not unique result, panic
    if len(found) != 1:
        raise ValueError("unique NDS2 channel match not found for %r"
                         % name)

    return found