Example
>>> from diem import jsonrpc, testnet
>>> client = jsonrpc.Client(testnet.JSON_RPC_URL)
>>> client.get_metadata()
version: 3300304
timestamp: 1601492912847973
chain_id: 2
>>> from diem import jsonrpc, testnet
>>> client = jsonrpc.Client(testnet.JSON_RPC_URL)
>>> client.get_metadata()
version: 3300304
timestamp: 1601492912847973
chain_id: 2