llama_index PromptHelper Issue in custom script

i am facing these 2 errors, kindly help me out what I am missing ?

_script.py", line 47, in
prompt_helper = PromptHelper(
TypeError: PromptHelper.init() got an unexpected keyword argument 'max_input_size'
_script.py", line 47, in
prompt_helper = PromptHelper(
TypeError: PromptHelper.init() got an unexpected keyword argument 'max_chunk_overlap'

#code

prompt_helper = PromptHelper(
# maximum input size
max_input_size=2048,
# number of output tokens
num_output=256,
# the maximum overlap between chunks.
max_chunk_overlap=20,
)