human
function providing default as null value.
assistant
Here is a Python code for providing default as null value

import numpy as np

def func(x, y=None):
    """
    A function with default value.
    """
    if y is None:
        return x
    else:
        return x + y

# Enter the x and y values
x = 10
y = 20

# Calling the function
print((func(x, y)))

#Example Output
# 30

#Remember to inspect code for bugs.