code: def _calc_projection_1group(x, mean, eps):
      spatial_ndim = len(x.shape[2:])
      spatial_axis = tuple(range(2, 2 + spatial_ndim))
      b, C = x.shape[:2]
      m = b
      for i in spatial_axis:
          m *= x.shape[i]
  
      x_hat = x.transpose((1, 0) + spatial_axis).reshape(C, -1)
      mean = x_hat.mean(axis=1)
      x_hat = x_hat - mean[:, None]
      cov = x_hat.dot(x_hat.T) / m + eps * numpy.eye(C, dtype=x.dtype)
      eigvals, eigvectors = numpy.linalg.eigh(cov)
      projection = eigvectors.dot(numpy.diag(eigvals**-0.5)).dot(
          eigvectors.T
      )
      return projection
  
imports: import contextlib
  import os
  import tempfile
  import unittest
  import numpy
  import chainer
  from chainer import links
  from chainer import testing
label_desc: Use image node_id 4 for calling a global function with example usage: _calc_projection_1group(x, mean, eps) and returns: projection