* A fix regarding the compatibility with python 2.6
the syntax of {n: self.attr(n) for n in attr_names} is illegal in python 2.6
* Update core.py
add a space after comma
* A fix regarding the compatibility with python 2.6
the syntax of {n: self.attr(n) for n in attr_names} is illegal in python 2.6
* Update core.py
add a space after comma