code: def lowpass(self, frequency, q=0.707):
          
          self.command.append('lowpass')
          self.command.append(frequency)
          self.command.append(str(q) + 'q')
          return self
docs: lowpass takes 2 parameters: filter frequency in Hz above which
          frequencies will be attenuated and q (default=0.707).
  
          Beware of clipping when using high q values.