Fix 159: check-docstring-first shall ignore attribute docstring at module top level

Now attribute docstrings no longer complain.
https://peps.python.org/pep-0257/#what-is-a-docstring

pre_commit_hooks/check_docstring_first.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import argparse
+import ast
 import io
 import tokenize
 from tokenize import tokenize as tokenize_tokenize
@@ -12,6 +13,14 @@ NON_CODE_TOKENS = frozenset((
 ))
 
 
+def _push_code(seen_code: io.StringIO, tok_type: int, text: str):
+    if tok_type == tokenize.ENCODING:
+        return
+    seen_code.write(text)
+    if text and not text.isspace():
+        seen_code.write(" ")
+
+
 def check_docstring_first(src: bytes, filename: str = '<unknown>') -> int:
     """Returns nonzero if the source has what looks like a docstring that is
     not at the beginning of the source.
@@ -21,12 +30,18 @@ def check_docstring_first(src: bytes, filename: str = '<unknown>') -> int:
     """
     found_docstring_line = None
     found_code_line = None
+    seen_code = io.StringIO()
 
     tok_gen = tokenize_tokenize(io.BytesIO(src).readline)
     for tok_type, _, (sline, scol), _, _ in tok_gen:
         # Looks like a docstring!
         if tok_type == tokenize.STRING and scol == 0:
             if found_docstring_line is not None:
+                tree = ast.parse(seen_code.getvalue())
+                assignments = ast.AnnAssign, ast.Assign, ast.AugAssign
+                if tree.body and isinstance(tree.body[-1], assignments):
+                    return 0
+
                 print(
                     f'{filename}:{sline}: Multiple module docstrings '
                     f'(first docstring on line {found_docstring_line}).',
@@ -41,7 +56,10 @@ def check_docstring_first(src: bytes, filename: str = '<unknown>') -> int:
             else:
                 found_docstring_line = sline
         elif tok_type not in NON_CODE_TOKENS and found_code_line is None:
+            _push_code(seen_code, tok_type, text)
             found_code_line = sline
+        else:
+            _push_code(seen_code, tok_type, text)
 
     return 0