def split(self):
        """split the full package name in list of compontents traditionally
        done by setuptools.find_packages. This routine skips any directories
        with __init__.py, for which the name starts with "_" or ".", or contain a
        setup.py/tox.ini (indicating a subpackage)
        """
        skip = []
        if self._split is None:
            fpn = self.full_package_name.split('.')
            self._split = []
            while fpn:
                self._split.insert(0, '.'.join(fpn))
                fpn = fpn[:-1]
            for d in sorted(os.listdir('.')):
                if not os.path.isdir(d) or d == self._split[0] or d[0] in '._':
                    continue
                # prevent sub-packages in namespace from being included
                x = os.path.join(d, '__init__.py')
                if os.path.exists(x):
                    pd = _package_data(x)
                    if pd.get('nested', False):
                        skip.append(d)
                        continue
                    self._split.append(self.full_package_name + '.' + d)
            if sys.version_info < (3,):
                self._split = [
                    (y.encode('utf-8') if isinstance(y, unicode) else y) for y in self._split
                ]
        if skip:
            # this interferes with output checking
            # print('skipping sub-packages:', ', '.join(skip))
            pass
        return self._split
split the full package name in list of compontents traditionally
        done by setuptools.find_packages. This routine skips any directories
        with __init__.py, for which the name starts with "_" or ".", or contain a
        setup.py/tox.ini (indicating a subpackage)
        
dynaconf/vendor/ruamel/yaml/setup.py