Funções do post sobre como documentar seu código.

main.py

def calculate_compound_interest_investment(
        principal_amount: float, rate: float, time: int
) -> float:
    """
    Returns the compound interest an accrued amount that includes
    principal plus interest.

    :param principal_amount: float
    :param rate: float
    :param time: int

    :return float principal_amount * (1 + rate)**time
    """
    return principal_amount * (1 + rate) ** time


def calculate_simple_interest_investment(principal_amount: float, rate: float, time: int) -> float:
    """
    Returns the simple interest an accrued amount that includes
    principal plus interest.

    :param principal_amount: float
    :param rate: float
    :param time: int

    :return float principal_amount * (1 + rate * time):
    """
    return principal_amount * (1 + rate * time)