code: static BasicDBObject[] getDocumentListFromCollection(Metamodel metaModel, Collection coll, Set<Attribute> columns,
              String tableName) throws PropertyAccessException
      {
          BasicDBObject[] dBObjects = new BasicDBObject[coll.size()];
          int count = 0;
          for (Object o : coll)
          {
              dBObjects[count] = (BasicDBObject) getDocumentFromObject(metaModel, o, columns, tableName).values()
                      .toArray()[0];
              count++;
          }
          return dBObjects;
      }
docs: Creates a MongoDB document list from a given java collection. columns in
  the document correspond Columns provided as List.
  
  @param coll
  the coll
  @param columns
  the columns
  @return the document list from collection
  @throws PropertyAccessException
  the property access exception