code: def conjunction(x, vx, k):
      """Returns a conjunction statistic as the sum of the k lowest t-values
  
      Parameters
      ----------
      x: array of shape(nrows, ncols),
         effect matrix
      vx: array of shape(nrows, ncols),
          variance matrix
      k: int,
         number of subjects in the conjunction
  
      Returns
      -------
      t array of shape(nrows): conjunction statistic
      """
      t = np.sort(x / np.sqrt(np.maximum(vx, 1.0e-15)))
      cjt = np.sum(t[:, :k], 1)
      return cjt
  
imports: import numpy
  from nipy.io.nibcompat import get_affine
  from nipy.labs.spatial_models.discrete_domain import grid_domain_from_binary_array
label_desc: Use image node_id 7 for calling a global function with example usage: conjunction(x, vx, k) and returns: cjt