code: def parse_ast(source, filename=None):
      
      if isinstance(source, text_type) and sys.version_info[0] == 2:
          # ast.parse() on Python 2 doesn't like encoding declarations
          # in Unicode strings
          source = CODING_COOKIE_RE.sub(r'\1', source, 1)
      return ast.parse(source, filename or '<unknown>')
docs: Parse source into a Python AST, taking care of encoding.