Additional functions: Delete and Select

[Lisa999]

@classmethod
def delete(cls, where, **fields):
    pkey_field = cls.__fields__[0]
    assert len(where) == 1 and pkey_field in where
    #print("update:", where)

    db = cls.__db__.db
    pkey = where[pkey_field]
    del(db[pkey])
    db.flush()

@classmethod
def select(cls, **fields):
    for v in cls.__db__.db.values():
        row = cls.Row(*ujson.loads(v))
        i = 0
        for k in cls.__fields__:
            if k in fields:
               if row[i] == fields[k]:
                  yield row
            i += 1