[Python] Why does calling instance methods through class name need explicit self?

I'm trying to call a method both through an object and through the class itself.

class Management:
factory = "Youtube"

def getSalary(self, signature):
print("Salary is I don't Know")
print(f"Salary is {self.salary} \n {signature}")

# Create an object
man = Management()

# Set an attribute dynamically
man.salary = 30000

# Call method through object (works fine)
man.getSalary("thanks")

# Call method through class (this causes an error)
Management.getSalary(man)


When I run this, the first method call via the object works fine:

Salary is I don't Know
Salary is 30000
thanks


But the second call via the class:

Management.getSalary(man)


gives me this error:

TypeError: getSalary() missing 1 required positional argument: 'signature'


I thought passing man would be enough, and it would use the salary from the object and print the salary and signature as before.

I double-checked my indentation, method definition, and attribute assignment. Still the same error.

Why is Python giving this error when calling the method via the class, and how should I properly pass the arguments in this situation?

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