From 6a90ad4bacf923c88438da53219c48355b847ed3 Mon Sep 17 00:00:00 2001
From: John Bauer <horatio@gmail.com>
Date: Wed, 14 Sep 2022 12:12:54 -0700
Subject: Hide the imports of SiLU and Mish from older versions of torch. 
 #1120

---
 stanza/models/constituency/utils.py | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/stanza/models/constituency/utils.py b/stanza/models/constituency/utils.py
index 5ae19f01..a11581dc 100644
--- a/stanza/models/constituency/utils.py
+++ b/stanza/models/constituency/utils.py
@@ -107,10 +107,17 @@ NONLINEARITY = {
     'relu':       nn.ReLU,
     'gelu':       nn.GELU,
     'leaky_relu': nn.LeakyReLU,
-    'silu':       nn.SiLU,
-    'mish':       nn.Mish,
 }
 
+# separating these out allows for backwards compatibility with earlier versions of pytorch
+# NOTE torch compatibility: if we ever *release* models with these
+# activation functions, we will need to break that compatibility
+if hasattr(nn, 'SiLU'):
+    NONLINEARITY['silu'] = nn.SiLU
+
+if hasattr(nn, 'Mish'):
+    NONLINEARITY['mish'] = nn.Mish
+
 def build_nonlinearity(nonlinearity):
     """
     Look up "nonlinearity" in a map from function name to function, build the appropriate layer.
-- 
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