JSONRPCProvider

(responseJSON: any): any => { 
    if (responseJSON.error !== undefined) { 
        if (responseJSON.error.code === -100 && responseJSON.error.message === 'Unknown block') { 
            throw new UnknownBlockError(); 
        } 
        throw new JSONRPCError(responseJSON.error); 
    } 
    return responseJSON.result; 
} 

public abstract request(req: JSONRPCRequest): Promise<JSONRPCResponse>;