input: Write a function to create a Spark context using given parameters.
  assert create_spark_context(master='local', appName='testApp').appName == 'testApp'
  assert create_spark_context(master='local', appName='anotherTest').master == 'local'
  assert create_spark_context(master='yarn', appName='distributedTest').appName == 'distributedTest'
output: def create_spark_context(master, appName):
      from pyspark import SparkConf, SparkContext
      conf = SparkConf().setMaster(master).setAppName(appName)
      sc = SparkContext(conf=conf)
      return sc