code: def _find_channel(connection, name, ctype, dtype, sample_rate, unique=False):
      
      # 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
docs: 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