Unique Elements

In this lab, you are tasked with writing a Python function named unique_elements. This function should take a list as input and return a new list that contains only the unique elements from the input list, preserving their original order.

Function Requirements:

• Input: A list of elements (can be of any type).
• Output: A new list with unique elements from the input list, maintaining the original order.

Examples:

1. Example 1:

   • Input: [1, 2, 2, 3, 3, 3, 4]
   • Output: [1, 2, 3, 4]
   • Here, duplicate elements 2 and 3 are removed.

2. Example 2:

   • Input: ["apple", "banana", "apple", "orange", "banana"]
   • Output: ["apple", "banana", "orange"]
   • In this case, the second occurrences of "apple" and "banana" are removed.

Edge Cases to Consider:

• Empty List: If the input list is empty, the function should return None.
• Type Validation: The function should only accept a list as input. If any other type of argument is passed, the function must raise a TypeError.

By carefully handling these scenarios and following the above requirements, you will create a function that effectively filters out duplicate elements while preserving the order of unique elements in a list.