Heat templates are invalid YAML

Issue

We are using online YAML validator to validate Heat templates and it is reporting it is not valid YAML file.

Validating following code, online YAML validators will throw error, however the code still works with Heat.

  BondInterfaceOvsOptions:
    default: ''
    description: The ovs_options string for the bond interface. Set things like
                 lacp=active and/or bond_mode=balance-slb using this option.
    type: string
  StorageNetworkVlanID:
    default: 30

Output from the online YAML validator:

Error : Unable to parse.
Line : 35               lacp=active and/or bond_mode=balance-slb using this option.