def __init__(self, ratio=<NUM_LIT:1>, knee=<NUM_LIT:0>, gain=<NUM_LIT:1>, enable=True):
<EOL>self.ratio = ratio<EOL>self.knee = knee<EOL>self.gain = gain<EOL>self.enable = enable<EOL>
:param float ratio: the compression ratio (1 means no compression).
    ratio should usually between 0 and 1.

:param float knee: the ratio where the compression starts to kick in.
    knee should usually be 0 <= knee <= ratio

:param float gain: post limiter output gain. gain should usually be >= 0