How does Serverless Resources refer a function in serverless.yml

Serverless Framework
1

I created a lambda function in serverless.yml like below:

functions:
must-run-1:
handler: main.run
name: must-run-1

under the resources, I have a Resource definition like this, how could I refer the function must-run-1 in the Resource definition? Below definition doesn’t work.

Resources:
ConditionStateMachine:
Type: AWS::StepFunctions::StateMachine
Properties:
StateMachineName: ConditionStateMachine
DefinitionString:
!Sub
- |-
{
“StartAt”: “HelloWorld”,
“States”: {
“HelloWorld”: {
“Type”: “Task”,
“Resource”: “${Func1Arn}”,
“End”: true
}
}
}
- {Func1Arn: “${self:functions.must-run-1}”}
RoleArn: arn:aws:iam::123456789:role/stepfunction-exec-role