human
list comprehension flatten.
assistant
Here is a Python program to return list comprehension flattening

import itertools

def flatten(l):
    """Returns a list of all elements in a nested list.

    Example:
        flatten([[1,2],[3,4]]) --> [1,2,3,4]
    """
    return [item for sublist in l for item in sublist]

# Enter the list
list_of_lists = [[1,2],[3,4]]

# Calling the function
print((flatten(list_of_lists)))

#Example Output
# [1, 2, 3, 4]

#Remember to inspect code for bugs.