This class is instantiated and invoked when an AST transformation is
activated. For Global AST Transformations, this interface is called once per SourceUnit, which is usually a
Groovy source file. For Local AST Transformations, this interface is invoked once every time the Local annotation
marker is encountered.
The method is invoked when an AST Transformation is active. For local transformations, it is invoked once
each time the local annotation is encountered. For global transformations, it is invoked once for every source
unit, which is typically a source file.
nodes - The ASTnodes when the call was triggered. Element 0 is the AnnotationNode that triggered this
annotation to be activated. Element 1 is the AnnotatedNode decorated, such as a MethodNode or ClassNode. For
global transformations it is usually safe to ignore this parameter.
source - The source unit being compiled. The source unit may contain several classes. For global transformations,
information about the AST can be retrieved from this object.