code: def instr(str, substr):
      
      sc = SparkContext._active_spark_context
      return Column(sc._jvm.functions.instr(_to_java_column(str), substr))
docs: Locate the position of the first occurrence of substr column in the given string.
      Returns null if either of the arguments are null.
  
      .. note:: The position is not zero based, but 1 based index. Returns 0 if substr
          could not be found in str.
  
      >>> df = spark.createDataFrame([('abcd',)], ['s',])
      >>> df.select(instr(df.s, 'b').alias('s')).collect()
      [Row(s=2)]