LeetCode #146 - LRU Cache: Design and implement a data structure for Least Recently Used (LRU) cache. It should support the following operations: get(key) and put(key, value). The order of the keys and the constraints on memory usage are crucial.

``` class LRUCache: def __init__(self, capacity: int): # Initialize the cache and its capacity def get(self, key: int) -> int: # Return the value of the key if the key exists in the cache, otherwise return -1 def put(self, key: int, value: int) -> None: # Update the value or insert the key-value pair if not already present ```