Update stafnet.py

Author: dylan-yin

ppsci/arch/stafnet.py

@@ -6,13 +6,9 @@
 import paddle
 from ppsci.arch import base
 try:
-    from pgl.nn.conv import GATv2Conv
-except ModuleNotFoundError as e:
-    logger.error("please install pgl with \'pip install pgl\'.") 
-    raise ModuleNotFoundError(str(e))
-    
-
-
+    import pgl
+except ModuleNotFoundError:
+    pass
 
 class Inception_Block_V1(paddle.nn.Layer):
     def __init__(self, in_channels, out_channels, num_kernels=6, init_weight=True):