@Override
  public <T> void registerRPCEndpoint(
      final String namespace,
      final String functionName,
      final Function<PluginRpcRequest, T> function) {
    checkArgument(namespace.matches("\\p{Alnum}+"), "Namespace must be only alpha numeric");
    checkArgument(functionName.matches("\\p{Alnum}+"), "Function Name must be only alpha numeric");
    checkNotNull(function);

    rpcMethods.put(namespace + "_" + functionName, function);
  }
Init the service

@param inProcessRpcMethods set of RPC methods that can be called
app/src/main/java/org/hyperledger/besu/services/RpcEndpointServiceImpl.java