make the sum function work with strings

[acesmeci]

Relevant code in src/utils.py:

def sum(a: int, b: int) -> int:
    '''
    This function returns the sum of two numbers

    Args:
    a: float the first number
    b: float the second number

    Returns:
    float the sum of a and b
    '''
    return a + b

Expected behavior: Be able to sum numbers with strings
Actual behavior: TypeError cannot sum str