dicts_union_preserve

def dicts_union_preserve(first_dict, second_dict):
    """
    Function that takes in two dictionaries as arguments, and returns a new dictionary that contains all key-value pairs from both input dictionaries.
    If a key already exists in the first dictionary, its value will be preserved instead of being overwritten.

    Args:
    first_dict (dict): The first dictionary to be merged
    second_dict (dict): The second dictionary to be merged

    Returns:
    dict: A new dictionary containing all key-value pairs from both input dictionaries

    Example:
    first_dict = {'a': 1, 'b': 2, 'c': 3}
    second_dict = {'c': 4, 'd': 5, 'e': 6}
    result = dicts_union_preserve(first_dict, second_dict)
    print(result) # {'a': 1, 'b': 2, 'c': 3, 'd': 5, 'e': 6}

    """
    # Create a new dictionary to store the union of key-value pairs
    union_dict = {}

    # Iterate through the key-value pairs in the first dictionary
    for key, value in first_dict.items():
        # Add the key-value pairs to the union dictionary
        union_dict[key] = value

    # Iterate through the key-value pairs in the second dictionary
    for key, value in second_dict.items():
        # Check if the key already exists in the union dictionary
        if key in union_dict:
            # If the key already exists, preserve the value from the first dictionary
            continue
        # If the key does not exist, add the key-value pair to the union dictionary
        union_dict[key] = value

    # Return the union dictionary
    return union_dict