How to use the handprint.files.is_url function in handprint

def _get(self, item, base_name, index):
        # Shortcuts to make the code more readable.
        output_dir = self._output_dir

        # For URLs, we download the corresponding files and name them with
        # the base_name.
        if is_url(item):
            # First make sure the URL actually points to an image.
            if __debug__: log('testing if URL contains an image: {}', item)
            try:
                response = urllib.request.urlopen(item)
            except Exception as ex:
                warn('Skipping URL due to error: {}', ex)
                return (None, None)
            if response.headers.get_content_maintype() != 'image':
                warn('Did not find an image at {}', item)
                return (None, None)
            orig_fmt = response.headers.get_content_subtype()
            base = '{}-{}'.format(base_name, index)
            # If we weren't given an output dir, then for URLs, we have no
            # choice but to use the current dir to download the file.
            # Important: don't change self._output_dir because if other
            # inputs *are* files, then those files will need other output dirs.

def targets_from_arguments(self, files, from_file):
        targets = []
        if from_file:
            if __debug__: log('reading {}', from_file)
            targets = filter(None, open(from_file).read().splitlines())
        else:
            for item in files:
                if is_url(item):
                    targets.append(item)
                elif path.isfile(item) and filename_extension(item) in ACCEPTED_FORMATS:
                    targets.append(item)
                elif path.isdir(item):
                    # It's a directory, so look for files within.
                    targets += files_in_directory(item, extensions = ACCEPTED_FORMATS)
                else:
                    warn('"{}" not a file or directory', item)

        # Filter files created in past runs.
        targets = filter(lambda name: '.handprint' not in name, targets)

        # If there is both a file in the format we generate and another
        # format of that file, ignore the other formats and just use ours.
        # Note: the value of targets is an iterator, but b/c it's tested inside
        # the loop, a separate list is needed (else get unexpected results).