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: return tables as string
  
  Returns
  -------
  csv : str
      concatenated summary tables in comma delimited format
docstr_tok: ["return","tables","as","string","Returns","--","--","--","-","csv",":","str","concatenated","summary","tables","in","comma","delimited","format"]
code: def as_csv(self):
      """return tables as string
  
      Returns
      -------
      csv : str
          concatenated summary tables in comma delimited format
  
      """
      csv = summary_return(self.tables, return_fmt="csv")
      if self.extra_txt is not None:
          csv = csv + "\n\n" + self.extra_txt
      return csv
  
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 11 for calling the Summary obj's underlying member method code with example usage: obj.as_csv() and returns: csv