code: def catstack(args):
      x = np.hstack(args)
      labels = np.hstack(
          [k * np.ones(len(arr)) for k, arr in enumerate(args)]
      )
      return x, labels
  
imports: from collections import namedtuple
  from statsmodels.compat.python import lzip, lrange
  import copy
  import math
  import numpy
  from numpy.testing import assert_almost_equal, assert_equal
  from scipy import stats, interpolate
  from statsmodels.iolib.table import SimpleTable
  from statsmodels.stats.multitest import multipletests, _ecdf, fdrcorrection, fdrcorrection_twostage
  from statsmodels.graphics import utils
  from statsmodels.tools.sm_exceptions import ValueWarning
label_desc: Use image node_id 6 for calling a global function with example usage: catstack(args) and returns: x,  labels