def _init_decoder(self):
        """
        Set-up the _decoder attribute if necessary.
        """
        # Note: content-encoding value should be case-insensitive, per RFC 7230
        # Section 3.2
        content_encoding = self.headers.get("content-encoding", "").lower()
        if self._decoder is None:
            if content_encoding in self.CONTENT_DECODERS:
                self._decoder = _get_decoder(content_encoding)
            elif "," in content_encoding:
                encodings = [
                    e.strip()
                    for e in content_encoding.split(",")
                    if e.strip() in self.CONTENT_DECODERS
                ]
                if len(encodings):
                    self._decoder = _get_decoder(content_encoding)

        Set-up the _decoder attribute if necessary.
        
product/gradle-plugin/src/main/python/pip/_vendor/urllib3/response.py