'Helper function for downloading test files
Will download and unzip the file into the directory self.path
Arguments:
filename (str): name of file to download from self.url
size (str): size of the file in bytes?
Returns:
str: Path to the downloaded dataset.'

def load_zip(self, filename, size):

    (workdir, filepath) = self._valid_path_append(self.path, '', filename)
    if (not os.path.exists(filepath)):
        self.fetch_dataset(self.url, filename, filepath, size)
    if ('.zip' in filepath):
        zip_ref = zipfile.ZipFile(filepath)
        zip_ref.extractall(workdir)
        zip_ref.close()
        filepath = filepath.split('.zip')[0]
    return filepath
