allow for process_record() while reading in avro

[gityow]

Feature request:
Could you allow for process_record function while reading in avro? Here is a suggestion.

def __file_to_dataframe(f, schema, process_record=None, **kwargs):

    reader = fastavro.reader(f, reader_schema=schema)
    records = list()
   if preprocess_record:
            records = [process_record(r) for r in avro_reader]
   else:
            records = list(avro_reader)

    return pd.DataFrame.from_records(records, **kwargs)