Make parser package private

Now that this is imported from the top level, make it private.

libcst/_parser/_python_parser.py

@@ -0,0 +1,48 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+#
+# This source code is licensed under the MIT license found in the
+# LICENSE file in the root directory of this source tree.
+
+from typing import Any, Iterable, Mapping, Sequence
+
+from parso.pgen2.generator import Grammar
+from parso.python.token import TokenType
+
+from libcst._parser._base_parser import BaseParser
+from libcst._parser._grammar import (
+    get_nonterminal_conversions,
+    get_terminal_conversions,
+)
+from libcst._parser._types.config import ParserConfig
+from libcst._parser._types.conversions import NonterminalConversion, TerminalConversion
+from libcst._parser._types.token import Token
+
+
+class PythonCSTParser(BaseParser[Token, TokenType, Any]):
+    config: ParserConfig
+    terminal_conversions: Mapping[str, TerminalConversion]
+    nonterminal_conversions: Mapping[str, NonterminalConversion]
+
+    def __init__(
+        self,
+        *,
+        tokens: Iterable[Token],
+        config: ParserConfig,
+        pgen_grammar: "Grammar[TokenType]",
+        start_nonterminal: str = "file_input",
+    ) -> None:
+        super().__init__(
+            tokens=tokens,
+            lines=config.lines,
+            pgen_grammar=pgen_grammar,
+            start_nonterminal=start_nonterminal,
+        )
+        self.config = config
+        self.terminal_conversions = get_terminal_conversions()
+        self.nonterminal_conversions = get_nonterminal_conversions()
+
+    def convert_nonterminal(self, nonterminal: str, children: Sequence[Any]) -> Any:
+        return self.nonterminal_conversions[nonterminal](self.config, children)
+
+    def convert_terminal(self, token: Token) -> Any:
+        return self.terminal_conversions[token.type.name](self.config, token)