class_docstr: class to keep track of Varma polynomial format
  
  
  Examples
  --------
  
  ar23 = np.array([[[ 1. ,  0. ],
                   [ 0. ,  1. ]],
  
                  [[-0.6,  0. ],
                   [ 0.2, -0.6]],
  
                  [[-0.1,  0. ],
                   [ 0.1, -0.1]]])
  
  ma22 = np.array([[[ 1. ,  0. ],
                   [ 0. ,  1. ]],
  
                  [[ 0.4,  0. ],
                   [ 0.2, 0.3]]])
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docstr: stack lagpolynomial horizontally in 2d array
  
          
docstr_tok: ["stack","lagpolynomial","horizontally","in","2d","array"]
code: def hstack(self, a=None, name="ar"):
      """stack lagpolynomial horizontally in 2d array"""
      if a is not None:
          a = a
      elif name == "ar":
          a = self.ar
      elif name == "ma":
          a = self.ma
      else:
          raise ValueError("no array or name given")
      return a.swapaxes(1, 2).reshape(-1, self.nvarall).T
  
imports: import numpy
  from scipy import signal
  from statsmodels.tsa.tsatools import lagmat
label_desc: Use image node_id 3 for calling the VarmaPoly obj's underlying member method code with example usage: obj.hstack(a, name) and returns: a