def __len__(self):
        return len(self._headers)
Returns the fully-formatted filename of what a new migration 'name' would be
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.2/django/core/servers/basehttp.py/Headers.__len__--crossover with--dataset/ETHPy150Open cloudera/hue/desktop/core/ext-py/South-1.0.2/south/migration/base.py/Migrations.next_filename