not able to collect dag

[manwapri]

import pyethash

with open("cache","rb") as fcache:
cache = fcache.read()

Using same block 0 from benchmark code

data_size = pyethash.get_full_size(0)

print("Generating dataset (DAG) of size %d." % data_size)
dataset = pyethash.calc_dataset_bytes(data_size, cache)

with open("dataset","w+b") as fcache:
fcache.write(dataset)

getting below error:
AttributeError: 'module' object has no attribute 'get_full_size'