code: def count_nonzero(self):
      return np.count_nonzero(self._deduped_data())
  
imports: from __future__ import division, print_function, absolute_import
  import numpy
  from .base import spmatrix, _ufuncs_with_fixed_point_at_zero
  from .sputils import isscalarlike, validateaxis, matrix
label_desc: Use image node_id 14 for calling the _data_matrix obj's underlying member method code with example usage: obj.count_nonzero() and returns: np