code: def _parse_cond(self, cond):
          
  
          CHANNEL_RX = CHANNEL_FMT_RX.format(CHANNEL_IDENTIFIER_RX)
  
          res = re.findall(CHANNEL_RX, cond)
          for ident in res:
              rx = CHANNEL_FMT_RX.format(ident)
              i = self._key(ident)  # integer key
  
              # repl = 'self(' + str(i) + ')'
              # Cannot be. Calls (__call__) can be replaced by nan. So must call
              # the array in the dict directly:
  
              repl = 'self.D[' + str(i) + ']'
              # %(<identifier>) replaced with self.D[i]
              cond = re.sub(rx, repl, cond)
          return cond
docs: Replace the format strings in cond with ``self.D[i]`` so it can
          be used in eval calls. Use ``CHANNEL_RX`` as pattern. Return the
          parsed string.
  
          This method should be exposed so that one can experiment with
          conditions and see that they are properly parsed.