我尝试以下代码：

import avro.schema
from avro.datafile import DataFileReader, DataFileWriter
from avro.io import DatumReader, DatumWriter
schema=avro.schema.parse(open('ff.avsc','rb').read())
reader = DatumReader(schema)
def decode(msg_value):
    message_bytes = io.BytesIO(msg_value)
    message_bytes.seek(5)
    decoder = BinaryDecoder(message_bytes)
    event_dict = reader.read(decoder)
    return event_dict
...
decode(message.value)

其中message.value是我来自Kafka的消息
出现错误

NameError: name 'BinaryDecoder' is not defined