code: def get(self, name, failobj=None):
          
          name = name.lower()
          for k, v in self._headers:
              if k.lower() == name:
                  return self.policy.header_fetch_parse(k, v)
          return failobj
docs: Get a header value.
  
          Like __getitem__() but return failobj instead of None when the field
          is missing.