code: def _getnnz(self, axis=None):
      if axis is not None:
          raise NotImplementedError(
              "_getnnz over an axis is not implemented "
              "for DIA format"
          )
      M, N = self.shape
      nnz = 0
      for k in self.offsets:
          if k > 0:
              nnz += min(M, N - k)
          else:
              nnz += min(M + k, N)
      return int(nnz)
  
imports: import numpy
  from ._matrix import spmatrix
  from ._base import issparse, _formats, _spbase, sparray
  from ._data import _data_matrix
  from ._sputils import isshape, upcast_char, getdtype, get_sum_dtype, validateaxis, check_shape
  from ._sparsetools import dia_matvec
label_desc: Use image node_id 5 for calling the _dia_base obj's underlying member method code with example usage: obj._getnnz(axis) and returns: int