Added "(object)" in graph_tools
Added "(object)" in graph_tools

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