The APIs available to the validation methods are:
getValueForColumn("<column name>")
Use this method to get the cell value for a given column
cell in the current row being edited by the user. For example, if the
user is editing the column cell Quantity at row 10, then to get the value
of another column cell Name at row 10, call the API as:
getValueForColumn("Name");
getColumnDataAtLevel()
Use this method to get all the cell values in the current
level under the immediate parent node.
getColumnDataAtLevel ();