class_docstr: :param headers:
      An iterable of field-value pairs. Must not contain multiple field names
      when compared case-insensitively.
  
  :param kwargs:
      Additional field-value pairs to pass in to ``dict.update``.
  
  A ``dict`` like container for storing HTTP Headers.
  
  Field names are stored and compared case-insensitively in compliance with
  RFC 7230. Iteration provides the first case-sensitive key seen for each
  case-insensitive pair.
  
  Using ``__setitem__`` syntax overwrites fields that compare equal
  case-insensitively in order to maintain ``dict``'s api. For fields that
  compare equal, instead create a new ``HTTPHeaderDict`` and use ``.add``
  in a loop.
  
  If multiple fields that are equal case-insensitively are passed to the
  constructor or ``.update``, the behavior is undefined and some will be
  lost.
  
  >>> headers = HTTPHeaderDict()
  >>> headers.add('Set-Cookie', 'foo=bar')
  >>> headers.add('set-cookie', 'baz=quxx')
  >>> headers['content-length'] = '7'
  >>> headers['SET-cookie']
  'foo=bar, baz=quxx'
  >>> headers['Content-Length']
  '7'
docstr: Iterate over all header lines, including duplicate ones.
docstr_tok: ["Iterate","over","all","header","lines",",","including","duplicate","ones","."]
code: def iteritems(self):
      """Iterate over all header lines, including duplicate ones."""
      for key in self:
          vals = self._container[key.lower()]
          for val in vals[1:]:
              yield vals[0], val
  
imports: import sys
  import requests
label_desc: Use image node_id 18 for calling the HTTPHeaderDict obj's underlying member method code with example usage: obj.iteritems() without return types