models: support building against PythonKit (#347)

Enable use of PythonKit and Python, preferring PythonKit over Python.

Author: compnerd

FastStyleTransfer/Demo/ColabDemo.ipynb

@@ -76,7 +76,11 @@
     "\n",
     "// Imaging capabilities\n",
     "%include \"EnableIPythonDisplay.swift\"\n",
-    "import Python\n",
+    "#if canImport(PythonKit)\n",
+    "    import PythonKit\n",
+    "#else",
+    "    import Python\n",
+    "#endif",
     "let plt = Python.import(\"matplotlib.pyplot\")\n",
     "IPythonDisplay.shell.enable_matplotlib(\"inline\")\n",
     "\n",
@@ -357,4 +361,4 @@
  },
  "nbformat": 4,
  "nbformat_minor": 1
-}
+}

Gym/Blackjack/main.swift

@@ -12,7 +12,11 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-import Python
+#if canImport(PythonKit)
+    import PythonKit
+#else
+    import Python
+#endif
 import TensorFlow
 
 let iterationCount = 10000

Gym/CartPole/main.swift

@@ -12,7 +12,11 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-import Python
+#if canImport(PythonKit)
+    import PythonKit
+#else
+    import Python
+#endif
 import TensorFlow
 
 // Force unwrapping with `!` does not provide source location when unwrapping `nil`, so we instead

Gym/FrozenLake/main.swift

@@ -12,7 +12,11 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-import Python
+#if canImport(PythonKit)
+    import PythonKit
+#else
+    import Python
+#endif
 import TensorFlow
 
 // Force unwrapping with `!` does not provide source location when unwrapping `nil`, so we instead

Transformer/Model.swift

@@ -13,7 +13,11 @@
 // limitations under the License.
 
 import TensorFlow
-import Python
+#if canImport(PythonKit)
+    import PythonKit
+#else
+    import Python
+#endif
 
 struct TimeDistributed: Layer {
     var dense: Dense<Float>

Transformer/main.swift

@@ -14,7 +14,11 @@
 
 import Foundation
 import ModelSupport
-import Python
+#if canImport(PythonKit)
+    import PythonKit
+#else
+    import Python
+#endif
 import TensorFlow
 import Transformer