code: def get_boundary(self, failobj=None):
          
          missing = object()
          boundary = self.get_param('boundary', missing)
          if boundary is missing:
              return failobj
          # RFC 2046 says that boundaries may begin but not end in w/s
          return utils.collapse_rfc2231_value(boundary).rstrip()
docs: Return the boundary associated with the payload if present.
  
          The boundary is extracted from the Content-Type header's `boundary'
          parameter, and it is unquoted.