added pg_setting_export_example_enhanced.py and new method list_vpgs_from_exported_settings in vpgs.py

venv/lib/python3.9/site-packages/pip/_internal/models/scheme.py

@@ -0,0 +1,31 @@
+"""
+For types associated with installation schemes.
+
+For a general overview of available schemes and their context, see
+https://docs.python.org/3/install/index.html#alternate-installation.
+"""
+
+
+SCHEME_KEYS = ['platlib', 'purelib', 'headers', 'scripts', 'data']
+
+
+class Scheme:
+    """A Scheme holds paths which are used as the base directories for
+    artifacts associated with a Python package.
+    """
+
+    __slots__ = SCHEME_KEYS
+
+    def __init__(
+        self,
+        platlib: str,
+        purelib: str,
+        headers: str,
+        scripts: str,
+        data: str,
+    ) -> None:
+        self.platlib = platlib
+        self.purelib = purelib
+        self.headers = headers
+        self.scripts = scripts
+        self.data = data