class_docstr: Result summary
  
  Construction does not take any parameters. Tables and text can be added
  with the `add_` methods.
  
  Attributes
  ----------
  tables : list of tables
      Contains the list of SimpleTable instances, horizontally concatenated
      tables are not saved separately.
  extra_txt : str
      extra lines that are added to the text output, used for warnings
      and explanations.
docstr: Add a double table, 2 tables with one column merged horizontally
  
  Parameters
  ----------
  res : results instance
      some required information is directly taken from the result
      instance
  title : str, optional
      if None, then a default title is used.
  gleft : list[tuple], optional
      elements for the left table, tuples are (name, value) pairs
      If gleft is None, then a default table is created
  gright : list[tuple], optional
      elements for the right table, tuples are (name, value) pairs
  yname : str, optional
      optional name for the endogenous variable, default is "y"
  xname : list[str], optional
      optional names for the exogenous variables, default is "var_xx".
      Must match the number of parameters in the model.
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code: def add_table_2cols(
      self,
      res,
      title=None,
      gleft=None,
      gright=None,
      yname=None,
      xname=None,
  ):
      """
      Add a double table, 2 tables with one column merged horizontally
  
      Parameters
      ----------
      res : results instance
          some required information is directly taken from the result
          instance
      title : str, optional
          if None, then a default title is used.
      gleft : list[tuple], optional
          elements for the left table, tuples are (name, value) pairs
          If gleft is None, then a default table is created
      gright : list[tuple], optional
          elements for the right table, tuples are (name, value) pairs
      yname : str, optional
          optional name for the endogenous variable, default is "y"
      xname : list[str], optional
          optional names for the exogenous variables, default is "var_xx".
          Must match the number of parameters in the model.
      """
  
      table = summary_top(
          res,
          title=title,
          gleft=gleft,
          gright=gright,
          yname=yname,
          xname=xname,
      )
      self.tables.append(table)
  
imports: from statsmodels.compat.python import lmap, lrange, lzip
  import copy
  from itertools import zip_longest
  import time
  import numpy
  from statsmodels.iolib.table import SimpleTable
  from statsmodels.iolib.tableformatting import fmt_2, fmt_2cols, fmt_params, gen_fmt
  from .summary2 import _model_types
label_desc: Use image node_id 6 for calling the Summary obj's underlying member method code with example usage: obj.add_table_2cols(res, title, gleft, gright, yname, xname) without return types