It looks good, but you implemented is_subset logic in the opposite way. you are supposed to find the if other_set is a subset of self set. so when you loop through, basically what you need to do is change
from
for ele in other_set_key:
if self.contains(ele):
count += 1
return count == other_set.size
to this
for ele in self.keys():
if not other_set.contains(ele):
return
is_subset
logic in the opposite way. you are supposed to find the if other_set is a subset of self set. so when you loop through, basically what you need to do is change fromto this