code: def _sum_outer(x):
      s = x.sum(axis=0)
      return np.outer(s, s)
  
file_path: metric-learn/metric_learn/lfda.py
imports: import numpy
  import scipy
  import warnings
  from sklearn.metrics import pairwise_distances
  from sklearn.base import TransformerMixin
  from ._util import _check_n_components
  from .base_metric import MahalanobisMixin
label_desc: Use image node_id 1 for calling a global function with example usage: _sum_outer(x) and returns: np