Define key in nlargest() of heapq?

[Davy]

Hi all,

I have a dictionary with n elements, and I want to get the m(m<=n)
keys with the largest values.

For example, I have dic that includes n=4 elements, I want m=2 keys
have the largest values)
dic = {0:4,3:1,5:2,7:8}
So, the the largest values are [8,4], so the keys are [7,0].

How to do this by nlargest() of heapq? I have tried
nlargest(2,dic,key),
the interpreter give out:
Traceback (most recent call last):
  File "<interactive input>", line 1, in <module>
NameError: name 'key' is not defined

Best regards,
Davy