Resolve a migration instance from a file.

        :param path: The path to factories directory
        :type path: str

        :param factory_file: The migration file
        :type factory_file: str

        :rtype: Factory

def _resolve(cls, path, factory_file):
        """
        Resolve a migration instance from a file.

        :param path: The path to factories directory
        :type path: str

        :param factory_file: The migration file
        :type factory_file: str

        :rtype: Factory
        """
        variables = {}

        name = factory_file
        factory_file = os.path.join(path, factory_file)

        with open(factory_file) as fh:
            exec(fh.read(), {}, variables)

        klass = variables[inflection.camelize(name)]

        instance = klass()

        return instance