locker: port base implementation from poetry

pyproject.toml

@@ -76,6 +76,14 @@ mypy_path = "src"
 files = "src, tests"
 exclude = "(?x)(^tests/.*/fixtures | ^src/poetry/core/_vendor)"
 
+check_untyped_defs = true
+#ignore_missing_imports = true
+show_error_codes = true
+#warn_redundant_casts = true
+#warn_unused_configs = true
+#warn_unused_ignores = true
+#files = "src"
+
 [[tool.mypy.overrides]]
 module = [
   'jsonschema.*',

src/poetry/core/lock/__init__.py

@@ -0,0 +1,6 @@
+from poetry.core.lock.locker import Locker
+
+
+__all__ = [
+    "Locker",
+]