code: public Function getFunction(String iface, String func) throws RpcException {
          Interface i = interfaces.get(iface);
          if (i == null) {
              String msg = "Interface '" + iface + "' not found";
              throw RpcException.Error.METHOD_NOT_FOUND.exc(msg);
          }
  
          Function f = i.getFunction(func);
          if (f == null) {
              String msg = "Function '" + iface + "." + func + "' not found";
              throw RpcException.Error.METHOD_NOT_FOUND.exc(msg);
          }
  
          return f;
      }
docs: Returns the Function associated with the given interface and function name.
  
  @param iface Interface name
  @param func Function name in the interface
  @return Function that matches iface and func on this Contract
  @throws RpcException If no Function matches