Move the grammar to a fitting file.

parso/grammar.py

@@ -2,7 +2,7 @@ import hashlib
 import os
 
 from parso._compatibility import FileNotFoundError, is_pypy
-from parso.pgen2.pgen import generate_grammar
+from parso.pgen2 import generate_grammar
 from parso.utils import split_lines, python_bytes_to_unicode, parse_version_string
 from parso.python.diff import DiffParser
 from parso.python.tokenize import tokenize_lines, tokenize

parso/pgen2/__init__.py

@@ -6,3 +6,5 @@
 # Licensed to PSF under a Contributor Agreement.
 # Copyright 2014 David Halter and Contributors
 # Modifications are dual-licensed: MIT and PSF.
+
+from parso.pgen2.generator import generate_grammar

test/test_pgen2.py

@@ -12,7 +12,7 @@ import pytest
 
 from parso import load_grammar
 from parso import ParserSyntaxError
-from parso.pgen2.pgen import generate_grammar
+from parso.pgen2 import generate_grammar
 from parso.python import tokenize