Lesson: stadistics exam, I cannot pass this lesson at the end


I have been passing all the exercises but at the end the platform tells me I have done something wrong and I cannot finished this lesson.I think there are not any problem with identation, the program tells me that is wrong "function varianza_notas"
This is my code, please help me:
notas = [100, 100, 90, 40, 80, 100, 85, 70, 90, 65, 90, 85, 50.5]

def print_calificaciones(calificaciones):
for calificacion in calificaciones:
print (calificacion)
print print_calificaciones(notas)

def notas_sum(calificaciones):
total = 0
for calificacion in calificaciones:
total += calificacion
return total
print notas_sum(notas)

def promedio_notas(calificaciones):
suma = notas_sum(calificaciones)
promedio = suma / float(len(calificaciones))
return promedio
print promedio_notas(notas)

def varianza_notas(calificaciones):
for calificacion in calificaciones:
return tota
print varianza_notas(notas)

def calificaciones_std_desviacion(varianza):
return varianza**0.5


print (calificaciones_std_desviacion(varianza))