def is_unknown(value):
    unk_vals = ['na', 'n/a', 'unk', 'unknown', '']
    try:
        if value.strip().lower() in unk_vals:
            return True
        else:
            return False
    except AttributeError:
        return False
    except TypeError:
        return False
Returns True if the value is a common unknown indicator:
dataset/ETHPy150Open kenfar/DataGristle/gristle/field_type.py/is_unknown