add default output for stylegan and fom (#501)

ppgan/models/firstorder_model.py

@@ -226,6 +226,8 @@ class FirstOrderModel(BaseModel):
         driving2 = {'value': value2, 'jacobian': j2}
         driving3 = {'value': value, 'jacobian': j}
 
+        if output_dir is None:
+            output_dir = 'inference_model'
         outpath = os.path.join(output_dir, "fom_dy2st")
         if not os.path.exists(outpath):
             os.makedirs(outpath)

ppgan/models/styleganv2_model.py

@@ -314,6 +314,8 @@ class StyleGAN2Model(BaseModel):
         infer_generator.set_generator(self.nets['gen'])
         style = paddle.rand(shape=inputs_size[0], dtype='float32')
         truncation = paddle.rand(shape=inputs_size[1], dtype='float32')
+        if output_dir is None:
+            output_dir = 'inference_model'
         paddle.jit.save(infer_generator,
                         os.path.join(output_dir, "stylegan2model_gen"),
                         input_spec=[style, truncation])