new_contents: import numpy as np
  from SimPEG.electromagnetics.natural_source.utils.data_utils import rec_to_ndarr
  
  
  def test_rec_to_ndarr():
      sample_rec_arr = np.ma.masked_array(data=[(1, 3), (2, 4)], dtype=[('a', int), ('b', float)])
      res = rec_to_ndarr(rec_arr=sample_rec_arr, data_type=float)
      exp_nd_array = np.array([[1, 3], [2, 4]], dtype=float)
      np.testing.assert_almost_equal(res, exp_nd_array)
  
subject: add test for rec_to_ndarr