def icon(value):
    value = str(value)

    if value.startswith('mdi:'):
        return value

    raise vol.Invalid('Icons should start with prefix "mdi:"')
test that fetching all of the data returns the correct results
dataset/ETHPy150Open home-assistant/home-assistant/homeassistant/helpers/config_validation.py/icon--crossover with--dataset/ETHPy150Open cloudera/hue/desktop/core/ext-py/cx_Oracle-5.1.2/test/StringVar.py/TestStringVar.testFetchAll