Optional. Named definitions of graphs, each pointing to a Python object.
Graphs can be StateGraph, @entrypoint, or any other Pregel object OR they can point to (async) context managers that accept a single configuration argument (of type RunnableConfig) and return a pregel object (instance of Stategraph, etc.).
Keys are graph names, values are "path/to/file.py:object_name". Example: { "mygraph": "graphs/my_graph.py:graph_definition", "anothergraph": "graphs/another.py:get_graph" }