Removed raise NotImplementedError, replace with pass.
Removed raise NotImplementedError, replace with pass.

agutieda/QuantEcon.py,QuantEcon/QuantEcon.py,jviada/QuantEcon.py,gxxjjj/QuantEcon.py,agutieda/QuantEcon.py,chenxulong/quanteco,oyamad/QuantEcon.py,dingliumath/quant-econ,jviada/QuantEcon.py,QuantEcon/QuantEcon.py,gxxjjj/QuantEcon.py,mgahsan/QuantEcon.py,oyamad/QuantEcon.py,mgahsan/QuantEcon.py,chenxulong/quanteco,andybrnr/QuantEcon.py,andybrnr/QuantEcon.py,dingliumath/quant-econ