full compatibility with torch models

* Network class added
* adding tests for Network class

pina/model/__init__.py

@@ -2,8 +2,10 @@ __all__ = [
     'FeedForward',
     'MultiFeedForward'
     'DeepONet',
+    'Network'
 ]
 
 from .feed_forward import FeedForward
 from .multi_feed_forward import MultiFeedForward
 from .deeponet import DeepONet
+from .network import Network