code: def trace_dot(X, Y):
      """Trace of np.dot(X, Y.T)."""
      return np.dot(X.ravel(), Y.ravel())
  
imports: from __future__ import division, print_function
  from math import sqrt
  import warnings
  import numbers
  import numpy
  import scipy.sparse
  from ..base import BaseEstimator, TransformerMixin
  from ..utils import check_random_state, check_array
  from ..utils.extmath import randomized_svd, safe_sparse_dot, squared_norm
  from ..utils.extmath import fast_dot
  from ..utils.validation import check_is_fitted, check_non_negative
  from ..utils import deprecated
  from ..exceptions import ConvergenceWarning
  from .cdnmf_fast import _update_cdnmf_fast
label_desc: Use image node_id 3 for calling a global function with example usage: trace_dot(X, Y) and returns: np