Target resource is not drawn when related to resources in the same layer

[a2ush]

Issue detail

Target resource is not drawn when related to resources in the same layer.

Reproduce process

Subnets are same layer in this template.
In this case, the ELB is a child resource of the two subnets, and then it is not rendered.

Yaml template

Resources:
  VPC1:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: !Ref VPCCIDR    
      EnableDnsSupport: true
      EnableDnsHostnames: true
  Subnet1:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC1
      MapPublicIpOnLaunch: false
  Subnet2:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC1
      MapPublicIpOnLaunch: false
  NLB: 
    Type: AWS::ElasticLoadBalancingV2::LoadBalancer
    Properties: 
      Scheme: "internal"
      Subnets: 
        - !Ref Subnet1    ## <------- here
        - !Ref Subnet2    ## <------- here
      Type: network

[a2ush]

workaround : comment out the subnets

Resources:
...
  NLB: 
    Type: AWS::ElasticLoadBalancingV2::LoadBalancer
    Properties: 
      Scheme: "internal"
      # Subnets: 
      #   - !Ref Subnet1
      #   - !Ref Subnet2

If you want to put the ELB icon into the VPC, you can describe it as the following;

Resources:
...
  NLB: 
    Type: AWS::ElasticLoadBalancingV2::LoadBalancer
    Properties: 
      Scheme: "internal"
      VpcId: !Ref VPC1

In CloudFormation, Resource type AWS::ElasticLoadBalancingV2::LoadBalancer does not have "VpcId" Property[1].
However, since awsdac just looks at dependencies based on !Ref or DependsOn, there is no problem in assigning non-existent properties to resources.

[1] https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-elasticloadbalancingv2-loadbalancer.html