def secure_filename(filename):
    r"""Borrowed from :mod:`werkzeug.utils`, under the BSD 3-clause license.

    Pass it a filename and it will return a secure version of it.  This
    filename can then safely be stored on a regular file system and passed
    to :func:`os.path.join`.  The filename returned is an ASCII only string
    for maximum portability.

    On windows systems the function also makes sure that the file is not
    named after one of the special device files.

    >>> secure_filename("My cool movie.mov")
    'My_cool_movie.mov'
    >>> secure_filename("../../../etc/passwd")
    'etc_passwd'
    >>> secure_filename(u'i contain cool \xfcml\xe4uts.txt')
    'i_contain_cool_umlauts.txt'

    The function might return an empty filename.  It's your responsibility
    to ensure that the filename is unique and that you generate random
    filename if the function returned an empty one.

    :param filename: the filename to secure
    """
    _filename_ascii_strip_re = re.compile(r'[^A-Za-z0-9_.-]')
    _windows_device_files = ('CON', 'AUX', 'COM1', 'COM2', 'COM3', 'COM4',
                             'LPT1', 'LPT2', 'LPT3', 'PRN', 'NUL')
    if isinstance(filename, text_type):
        from unicodedata import normalize
        filename = normalize('NFKD', filename).encode('ascii', 'ignore')
        if not PY2:
            filename = filename.decode('ascii')
    for sep in os.path.sep, os.path.altsep:
        if sep:
            filename = filename.replace(sep, ' ')
    filename = str(_filename_ascii_strip_re.sub('', '_'.join(
                   filename.split()))).strip('._')

    # on nt a couple of special files are present in each folder.  We
    # have to ensure that the target file is not such a filename.  In
    # this case we prepend an underline
    if os.name == 'nt' and filename and \
       filename.split('.')[0].upper() in _windows_device_files:
        filename = '_' + filename

    return filename
def select_mask(cls, dataset, selection):
        """
        Given a Dataset object and a dictionary with dimension keys and
        selection keys (i.e. tuple ranges, slices, sets, lists, or literals)
        return a boolean mask over the rows in the Dataset object that
        have been selected.
        """
        mask = None
        for dim, sel in selection.items():
            if isinstance(sel, tuple):
                sel = slice(*sel)
            arr = cls.values(dataset, dim, keep_index=True)
            if util.isdatetime(arr) and util.pd:
                try:
                    sel = util.parse_datetime_selection(sel)
                except:
                    pass

            new_masks = []
            if isinstance(sel, slice):
                with warnings.catch_warnings():
                    warnings.filterwarnings('ignore', r'invalid value encountered')
                    if sel.start is not None:
                        new_masks.append(sel.start <= arr)
                    if sel.stop is not None:
                        new_masks.append(arr < sel.stop)
                if not new_masks:
                    continue
                new_mask = new_masks[0]
                for imask in new_masks[1:]:
                    new_mask &= imask
            elif isinstance(sel, (set, list)):
                for v in sel:
                    new_masks.append(arr==v)
                if not new_masks:
                    continue
                new_mask = new_masks[0]
                for imask in new_masks[1:]:
                    new_mask |= imask
            elif callable(sel):
                new_mask = sel(arr)
            else:
                new_mask = arr == sel

            if mask is None:
                mask = new_mask
            else:
                mask &= new_mask
        return mask