'Returns True if this link can be verified after download, False if it
cannot, and None if we cannot determine.'

@property
def verifiable(self):

    trusted = (self.trusted or getattr(self.comes_from, 'trusted', None))
    if ((trusted is not None) and trusted):
        try:
            api_version = getattr(self.comes_from, 'api_version', None)
            api_version = int(api_version)
        except (ValueError, TypeError):
            api_version = None
        if ((api_version is None) or (api_version <= 1)):
            return
        if self.hash:
            return True
        else:
            return False
    elif (trusted is not None):
        return False
