code: def _reset_dtype(self):
      gs.set_default_dtype("float64")
  
imports: import random
  import numpy
  import pytest
  import scipy
  import geomstats.backend
  from geomstats.test.test_case import TestCase
  from geomstats.test.vectorization import generate_vectorization_data
label_desc: Use image node_id 1 for calling the DtypeTestCase obj's underlying member method code with example usage: obj._reset_dtype() without return types