--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/env/lib/python3.9/site-packages/setuptools/extension.py	Mon Mar 22 18:12:50 2021 +0000
@@ -0,0 +1,55 @@
+import re
+import functools
+import distutils.core
+import distutils.errors
+import distutils.extension
+
+from .monkey import get_unpatched
+
+
+def _have_cython():
+    """
+    Return True if Cython can be imported.
+    """
+    cython_impl = 'Cython.Distutils.build_ext'
+    try:
+        # from (cython_impl) import build_ext
+        __import__(cython_impl, fromlist=['build_ext']).build_ext
+        return True
+    except Exception:
+        pass
+    return False
+
+
+# for compatibility
+have_pyrex = _have_cython
+
+_Extension = get_unpatched(distutils.core.Extension)
+
+
+class Extension(_Extension):
+    """Extension that uses '.c' files in place of '.pyx' files"""
+
+    def __init__(self, name, sources, *args, **kw):
+        # The *args is needed for compatibility as calls may use positional
+        # arguments. py_limited_api may be set only via keyword.
+        self.py_limited_api = kw.pop("py_limited_api", False)
+        _Extension.__init__(self, name, sources, *args, **kw)
+
+    def _convert_pyx_sources_to_lang(self):
+        """
+        Replace sources with .pyx extensions to sources with the target
+        language extension. This mechanism allows language authors to supply
+        pre-converted sources but to prefer the .pyx sources.
+        """
+        if _have_cython():
+            # the build has Cython, so allow it to compile the .pyx files
+            return
+        lang = self.language or ''
+        target_ext = '.cpp' if lang.lower() == 'c++' else '.c'
+        sub = functools.partial(re.sub, '.pyx$', target_ext)
+        self.sources = list(map(sub, self.sources))
+
+
+class Library(Extension):
+    """Just like a regular Extension, but built as a library instead"""