Erro ao imprimir coluna!

Estou tendo um erro na coluna abaixo:

notas.groupby("filmeId").mean()["nota"]

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-42-dd6d1bcc4a2d> in <module>()
----> 1 notas.groupby("filmeId").mean()["nota"]

3 frames
/usr/local/lib/python3.6/dist-packages/pandas/core/groupby/grouper.py in _get_grouper(obj, key, axis, level, sort, observed, mutated, validate)
    576                 in_axis, name, level, gpr = False, None, gpr, None
    577             else:
--> 578                 raise KeyError(gpr)
    579         elif isinstance(gpr, Grouper) and gpr.key is not None:
    580             # Add key to exclusions

KeyError: 'filmeId'