private RexCall getUDTFFunction(ASTNode functionAST, RowResolver inputRR)
      throws SemanticException {

    String functionName = functionAST.getChild(0).getText().toLowerCase();

    // create the RexNode operands for the UDTF RexCall
    List<RexNode> operandsForUDTF = getOperandsForUDTF(functionAST, inputRR);

    return this.functionHelper.getUDTFFunction(functionName, operandsForUDTF);
  }
LateralViewPlan is a helper class holding the objects needed for generating a Calcite
plan from an ASTNode. The object is to be generated when a LATERAL_VIEW token is detected.
From the ASTNode and relevant input node information, the following objects are created:
* A HiveTableFunctionScan RelNode
* A RowResolver containing the row resolving information output from the RelNode
* The table alias for the table generated by the UDTF and Lateral View
ql/src/java/org/apache/hadoop/hive/ql/parse/relnodegen/LateralViewPlan.java