code: def counter(self, ch, part=None):
          
          return Counter(self(self._key(ch), part=part))
docs: Return a counter on the channel ch.
  
          ch: string or integer.
              The channel index number or channel name.
  
          part: int or None
              The 0-based enumeration of a True part to return. This
              has an effect whether or not the mask or filter is turned
              on. Raise IndexError if the part does not exist.
  
          See `Counter
          <https://docs.python.org/2.7/library/collections.html#counter-objects>`_
          for the counter object returned.