class_docstr: This class wraps data into a dict-like object
docstr: :param mask: boolean mask
  :return: a DataAccessObject with a subset of rows matching mask
docstr_tok: [":","param","mask",":","boolean","mask",":","return",":","a","DataAccessObject","with","a","subset","of","rows","matching","mask"]
code: def where(self, mask):
      """
      :param mask: boolean mask
      :return: a DataAccessObject with a subset of rows matching mask
      """
      assert len(mask) == len(self)
      return DataAccessObject(
          {k: self.dict[k][mask] for k in self.dict}
      )
  
imports: from collections import defaultdict
  import csv
  from datetime import datetime
  import json
  from math import radians, cos, sin, asin, sqrt
  import urllib2
  import numpy
label_desc: Use image node_id 7 for calling the DataAccessObject obj's underlying member method code with example usage: obj.where(mask) and returns: DataAccessObject