code: def _prepare_default_dtype(src_array, dtype):
      
      if dtype is None:
          if isinstance(src_array, (NDArray, np.ndarray)):
              dtype = src_array.dtype
          elif spsp and isinstance(src_array, spsp.csr.csr_matrix):
              dtype = src_array.dtype
          else:
              dtype = mx_real_t
      return dtype
docs: Prepare the value of dtype if `dtype` is None. If `src_array` is an NDArray, numpy.ndarray
      or scipy.sparse.csr.csr_matrix, return src_array.dtype. float32 is returned otherwise.