public static UnifiedVariableDefinitionList ToVariableDefinitionList(
     this UnifiedVariableDefinition singleton)
 {
     if (singleton == null)
     {
         return(UnifiedVariableDefinitionList.Create());
     }
     return(UnifiedVariableDefinitionList.Create(singleton));
 }
 public static UnifiedVariableDefinitionList ToVariableDefinitionList(
     this IEnumerable <UnifiedVariableDefinition> expressions)
 {
     return(UnifiedVariableDefinitionList.Create(expressions));
 }