Creating the Signature Class

In this task, write the code for the operator. A custom operator must implement three classes: the signature, the GUI node, and the runtime. Each of these classes defines behavior and information that the TIBCO Data Science - Team Studio workflow engine uses to execute the operator.

Procedure
1. Create a class called SimpleDatasetGeneratorSignature and have it extend OperatorSignature.
   For the type parameters, include SimpleDatasetGeneratorGUINode and SimpleDatasetGeneratorRuntime, both of which are described in Creating the GUI Node Class.
2. Add one function called getMetadata().
   This function describes the metadata about your operator. The code for this part should resemble the following:

   class SimpleDatasetGeneratorSignature extends OperatorSignature[
     SimpleDatasetGeneratorGUINode,
     SimpleDatasetGeneratorRuntime] {
     def getMetadata: OperatorMetadata = {
       new OperatorMetadata(
         name = "Sample - Simple Data Generator", // a name for your operator
         category = "Plugin Sample - Spark",      // a category for the operator (seen on the Alpine web application)
         author = Some("My Name"),                     // the author's name
         version = 1,                             // a version number
         helpURL = None,                           // a link to documentation about the operator, if available
         icon = None,                      // an OperatorIcon object for a custom icon (optional)
         toolTipText = Some("An operator that generates a dataset with user-specified number of rows.")
       )
     }
   }