Missing `def` keyword in groovy

[llxia]

Noticed the following warning messages in the Jenkins job.

Did you forget the `def` keyword? WorkflowScript seems to be setting a field named SPEC (to a value of type String) which could lead to memory leaks or other issues.
Did you forget the `def` keyword? WorkflowScript seems to be setting a field named dockerAgents (to a value of type ArrayList) which could lead to memory leaks or other issues.
Did you forget the `def` keyword? WorkflowScript seems to be setting a field named dockerAgentLabel (to a value of type String) which could lead to memory leaks or other issues.
Did you forget the `def` keyword? WorkflowScript seems to be setting a field named LABEL (to a value of type String) which could lead to memory leaks or other issues.
Did you forget the `def` keyword? WorkflowScript seems to be setting a field named LABEL (to a value of type String) which could lead to memory leaks or other issues.
...
Did you forget the `def` keyword? WorkflowScript seems to be setting a field named dynamicAgents (to a value of type ArrayList) which could lead to memory leaks or other issues.