'place an env in the env var list'

def update_volume(self, volume):

    exist_volumes = self.get_volumes()
    if (not volume):
        return False
    update_idx = None
    for (idx, exist_vol) in enumerate(exist_volumes):
        if (exist_vol['name'] == volume['name']):
            update_idx = idx
            break
    if (update_idx != None):
        exist_volumes[update_idx] = volume
    else:
        self.add_volume(volume)
    return True
