docstr: add an option to this group.
  
  if a shortened version of a long option is specified it will
  be suppressed in the help. addoption('--twowords', '--two-words')
  results in help showing '--two-words' only, but --twowords gets
  accepted **and** the automatic destination is in args.twowords
docstr_tok: ["add","an","option","to","this","group",".","if","a","shortened","version","of","a","long","option","is","specified","it","will","be","suppressed","in","the","help",".","addoption","(","'","--","twowords","'",",","'","--","two-words","'",")","results","in","help","showing","'","--","two-words","'","only",",","but","--","twowords","gets","accepted","*","*","and","*","*","the","automatic","destination","is","in","args.twowords"]
code: def addoption(self, *optnames, **attrs):
      """add an option to this group.
  
      if a shortened version of a long option is specified it will
      be suppressed in the help. addoption('--twowords', '--two-words')
      results in help showing '--two-words' only, but --twowords gets
      accepted **and** the automatic destination is in args.twowords
      """
      conflict = set(optnames).intersection(
          name for opt in self.options for name in opt.names()
      )
      if conflict:
          raise ValueError("option names %s already added" % conflict)
      option = Argument(*optnames, **attrs)
      self._addoption_instance(option, shortupper=False)
  
imports: import argparse
  import warnings
  import py
  import six
  from _pytest.config.exceptions import UsageError
label_desc: Use image node_id 2 for calling the OptionGroup obj's underlying member method code with example usage: obj.addoption() without return types