@property
    def size(self):
        return sum([cidr.size for cidr in self._cidrs])
Given an environment, returns a string looking like
dataset/ETHPy150Open drkjam/netaddr/netaddr/ip/sets.py/IPSet.size--crossover with--dataset/ETHPy150Open adobe/brackets-shell/gyp/pylib/gyp/generator/ninja.py/NinjaWriter.ComputeExportEnvString