code: def dot(self, x, y):
      if is_sparse(x) or is_sparse(y):
          return sparse.dot(x, y)
      return np.dot(x, y)
  
imports: from copy import copy
  from packaging.version import Version
  import numpy
  import scipy
  import scipy.linalg
  import scipy.sparse.linalg
  import sparse
  from .None import register_sparse_backend
  from ....backend.core import Backend
label_desc: Use image node_id 8 for calling the NumpySparseBackend obj's underlying member method code with example usage: obj.dot(x, y) and returns: np, sparse