"""
    Rename this file from list_op_shell.py to list_op.py and write the function bodies below.
"""
def average(num_list):
    """
    Returns the average of numbers in a list.
    Returns 0 for an empty list.
    Replace "pass" with your code below and remove this comment line.
    """
    pass
    
def remove_duplicates(num_list):
    """
    Returns a list with duplicate elements removed.  
    Replace "pass" with your code below and remove this comment line.
    """
    pass

def count_greater_occurrences(num_list, threshold):
    """
    Counts the occurrences of elements in a list that is greater than a specific threshold.
    Replace "pass" with your code below and remove this comment line.
    """
    pass
    
def sum_squares(num_list):
    """
    Returns the sum of squares of numbers in a list.
    Replace "pass" with your code below and remove this comment line.
    """
    pass