| arguments | The variables that are passed to the parametric mixin. Arguments are optional. |
| is-negation | This indicates whether the guard condition is a not condition or not. For example when not (@type = error) means the mixin will be used whenever the value of @type is not error. |
| ref-variable | This is the variable whose value determines which mixin's properties should be applied to the element. This is mandatory. |
| operator | This is the operator that is used for evaluating the condition. It can be =, >, <, >=, <=. This is not mandatory. When the operator and value is not given, the compiler assumes the condition to be <ref-variable> = true. |
| value | The value that is used for evaluating the condition. This is optional but becomes mandatory when an operator is provided. |
