safe_eval.SafeEvalCodeException:
Exception class for reporting all errors which occured while
validating AST for source code in safe_eval().
safe_eval.SafeEvalContextException:
Exception class for reporting unallowed objects found in the dict
intended to be used as the local enviroment in safe_eval().
safe_eval.SafeEvalVisitor:
Data-driven visitor which walks the AST for some code and makes
sure it doesn't contain any expression/statements which are
declared as restricted in 'unallowed_ast_nodes'.