class_docstr: Sparse matrix where rows and columns are indexed using string.
  
  This matrix is used to store resutls of the competition evaluation.
class_docstr_tok: ["Sparse","matrix","where","rows","and","columns","are","indexed","using","string",".","This","matrix","is","used","to","store","resutls","of","the","competition","evaluation","."]
docstr: Initializes empty matrix.
docstr_tok: ["Initializes","empty","matrix","."]
code: def __init__(self, default_value=0):
      """Initializes empty matrix."""
      self._items = {}
      self._dim0 = set()
      self._dim1 = set()
      self._default_value = default_value
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import csv
  from io import BytesIO
  from io import StringIO
  import logging
  import os
  import pickle
  import time
  from six import iteritems
  from six import iterkeys
  from six import itervalues
  from six import PY3
label_desc: Use image node_id 1 to create a new ResultMatrix object from inherited base classes: object with example: obj = ResultMatrix(default_value)