def _cast(self, out, peek=None):
        """ Try to convert the parameter into something WSGI compatible and set
        correct HTTP headers when possible.
        Support: False, str, unicode, dict, HTTPResponse, HTTPError, file-like,
        iterable of strings and iterable of unicodes
        """

        # Empty output is done here
        if not out:
            if 'Content-Length' not in response:
                response['Content-Length'] = 0
            return []
        # Join lists of byte or unicode strings. Mixed lists are NOT supported
        if isinstance(out, (tuple, list))\
        and isinstance(out[0], (bytes, unicode)):
            out = out[0][0:0].join(out)  # b'abc'[0:0] -> b''
        # Encode unicode strings
        if isinstance(out, unicode):
            out = out.encode(response.charset)
        # Byte Strings are just returned
        if isinstance(out, bytes):
            if 'Content-Length' not in response:
                response['Content-Length'] = len(out)
            return [out]
        # HTTPError or HTTPException (recursive, because they may wrap anything)
        # TODO: Handle these explicitly in handle() or make them iterable.
        if isinstance(out, HTTPError):
            out.apply(response)
            out = self.error_handler.get(out.status_code,
                                         self.default_error_handler)(out)
            return self._cast(out)
        if isinstance(out, HTTPResponse):
            out.apply(response)
            return self._cast(out.body)

        # File-like objects.
        if hasattr(out, 'read'):
            if 'wsgi.file_wrapper' in request.environ:
                return request.environ['wsgi.file_wrapper'](out)
            elif hasattr(out, 'close') or not hasattr(out, '__iter__'):
                return WSGIFileWrapper(out)

        # Handle Iterables. We peek into them to detect their inner type.
        try:
            iout = iter(out)
            first = next(iout)
            while not first:
                first = next(iout)
        except StopIteration:
            return self._cast('')
        except HTTPResponse:
            first = _e()
        except (KeyboardInterrupt, __HOLE__, MemoryError):
            raise
        except:
            if not self.catchall: raise
            first = HTTPError(500, 'Unhandled exception', _e(), format_exc())

        # These are the inner types allowed in iterator or generator objects.
        if isinstance(first, HTTPResponse):
            return self._cast(first)
        elif isinstance(first, bytes):
            new_iter = itertools.chain([first], iout)
        elif isinstance(first, unicode):
            encoder = lambda x: x.encode(response.charset)
            new_iter = imap(encoder, itertools.chain([first], iout))
        else:
            msg = 'Unsupported response type: %s' % type(first)
            return self._cast(HTTPError(500, msg))
        if hasattr(out, 'close'):
            new_iter = _closeiter(new_iter, out.close)
        return new_iter
dataset/ETHPy150Open Arelle/Arelle/arelle/webserver/bottle.py/Bottle._cast