def _read_data(cls, input_file):
    """Reads a BIO data."""
    with open(input_file) as f:
        lines = []
        words = []
        labels = []
        for line in f:
            contends = line.strip()
            word = line.strip().split(' ')[0]
            label = line.strip().split(' ')[-1]
            if contends.startswith('-DOCSTART-'):
                words.append('')
                continue
            if len(contends) == 0:
                l = ' '.join([label for label in labels if len(label) > 0])
                w = ' '.join([word for word in words if len(word) > 0])
                lines.append([l, w])
                words = []
                labels = []
                continue
            words.append(word)
            labels.append(label)
        return lines
