Handle fields that clash with Python reserved keywords

betterproto/casing.py

@@ -0,0 +1,41 @@
+import stringcase
+
+
+def safe_snake_case(value: str) -> str:
+    """Snake case a value taking into account Python keywords."""
+    value = stringcase.snakecase(value)
+    if value in [
+        "and",
+        "as",
+        "assert",
+        "break",
+        "class",
+        "continue",
+        "def",
+        "del",
+        "elif",
+        "else",
+        "except",
+        "finally",
+        "for",
+        "from",
+        "global",
+        "if",
+        "import",
+        "in",
+        "is",
+        "lambda",
+        "nonlocal",
+        "not",
+        "or",
+        "pass",
+        "raise",
+        "return",
+        "try",
+        "while",
+        "with",
+        "yield",
+    ]:
+        # https://www.python.org/dev/peps/pep-0008/#descriptive-naming-styles
+        value += "_"
+    return value