The langgraph-checkpoint  library defines the base interface for LangGraph
checkpointers. Checkpointers provide a persistence layer for LangGraph.
They allow you to interact with and manage the graph's state. When you use
a graph with a checkpointer, the checkpointer saves a checkpoint of the
graph state at every superstep, enabling several powerful capabilities like
human-in-the-loop, "memory" between interactions and more.
