Pyspark Flatten json

from pyspark.sql.types import *
from pyspark.sql.functions import *

#Flatten array of structs and structs
def flatten(df):
   # compute Complex Fields (Lists and Structs) in Schema   
   complex_fields = dict([(field.name, field.dataType)
                             for field in df.schema.fields
                             if type(field.dataType) == ArrayType or  type(field.dataType) == StructType])
   while len(complex_fields)!=0:
      col_name=list(complex_fields.keys())[0]
      print ("Processing :"+col_name+" Type : "+str(type(complex_fields[col_name])))
    
      # if StructType then convert all sub element to columns.
      # i.e. flatten structs
      if (type(complex_fields[col_name]) == StructType):
         expanded = [col(col_name+'.'+k).alias(col_name+'_'+k) for k in [ n.name for n in  complex_fields[col_name]]]
         df=df.select("*", *expanded).drop(col_name)
    
      # if ArrayType then add the Array Elements as Rows using the explode function
      # i.e. explode Arrays
      elif (type(complex_fields[col_name]) == ArrayType):    
         df=df.withColumn(col_name,explode_outer(col_name))
    
      # recompute remaining Complex Fields in Schema       
      complex_fields = dict([(field.name, field.dataType)
                             for field in df.schema.fields
                             if type(field.dataType) == ArrayType or  type(field.dataType) == StructType])
   return df

df=flatten(df)
df.printSchema()

This function flatten(), fails when there is nested array inside array, It failed to flatten these, "user_mentions": [
{
"screen_name": "AshJone15461246",
"name": "Ash Jones",
"id": 1589564629369462800,
"id_str": "1589564629369462784",
"indices": [
0,
16
]
},
{
"screen_name": "BariAWilliams",
"name": "Bärí A. Williams, Esq.",
"id": 4639656854,
"id_str": "4639656854",
"indices": [
17,
31
]
},
{
"screen_name": "bjorn_hefnoll",
"name": "Björn",
"id": 1374096417954881500,
"id_str": "1374096417954881548",
"indices": [
32,
46
]
},
{
"screen_name": "SpencerAlthouse",
"name": "Spencer Althouse",
"id": 38307346,
"id_str": "38307346",
"indices": [
47,
63
]
}
].