Autodetect the file system on the remote device. Used by SCP operations.

def _autodetect_fs(self, cmd="dir", pattern=r"Directory of (.*)/"):
        """Autodetect the file system on the remote device. Used by SCP operations."""
        if not self.check_enable_mode():
            raise ValueError("Must be in enable mode to auto-detect the file-system.")
        output = self.send_command_expect(cmd)
        match = re.search(pattern, output)
        if match:
            file_system = match.group(1)
            # Test file_system
            cmd = "dir {}".format(file_system)
            output = self.send_command_expect(cmd)
            if "% Invalid" in output or "%Error:" in output:
                raise ValueError(
                    "An error occurred in dynamically determining remote file "
                    "system: {} {}".format(cmd, output)
                )
            else:
                return file_system

        raise ValueError(
            "An error occurred in dynamically determining remote file "
            "system: {} {}".format(cmd, output)
        )