我的代码spark2.4和python-3声明如下，带有spark上下文，但总是失败，出现以下错误。
是什么，我都错过了申报。
错误： java.lang.IllegalStateException ：用户未初始化spark上下文！。

# lib imported

from pyspark.sql import SparkSession
from pyspark.context import SparkContext
from awsglue.context import GlueContext
from awsglue.job import Job
from awsglue.utils import getResolvedOptions
import pyspark.sql.functions as F
from datetime import datetime
from pyspark.sql.utils import AnalysisException

main():
{  

# Initialize start of the Glue job

sc = SparkContext()
glueContext = GlueContext(sc.getOrCreate())
spark = glueContext.spark_session
job = Job(glueContext)
job.init(args['JOB_NAME'],args)

}