parse pascal voc record into a dictionary
    :param filename: xml file path
    :return: list of dict

def parse_voc_rec(filename):
    """
    parse pascal voc record into a dictionary
    :param filename: xml file path
    :return: list of dict
    """
    import xml.etree.ElementTree as ET
    tree = ET.parse(filename)
    objects = []
    for obj in tree.findall('object'):
        obj_dict = dict()
        obj_dict['name'] = obj.find('name').text
        obj_dict['difficult'] = int(obj.find('difficult').text)
        bbox = obj.find('bndbox')
        obj_dict['bbox'] = [int(bbox.find('xmin').text),
                            int(bbox.find('ymin').text),
                            int(bbox.find('xmax').text),
                            int(bbox.find('ymax').text)]
        objects.append(obj_dict)
    return objects