Check to see if a particular key exists within the bucket.
        Returns: An instance of a Key object or None

        :type key_name: string
        :param key_name: The name of the key to retrieve

        :type version_id: string
        :param version_id: Unused in this subclass.

        :type stream_type: integer
        :param stream_type: Type of the Key - Regular File or input/output Stream

        :rtype: :class:`boto.file.key.Key`
        :returns: A Key object from this bucket.

def get_key(self, key_name, headers=None, version_id=None,
                                            key_type=Key.KEY_REGULAR_FILE):
        """
        Check to see if a particular key exists within the bucket.
        Returns: An instance of a Key object or None

        :type key_name: string
        :param key_name: The name of the key to retrieve

        :type version_id: string
        :param version_id: Unused in this subclass.

        :type stream_type: integer
        :param stream_type: Type of the Key - Regular File or input/output Stream

        :rtype: :class:`boto.file.key.Key`
        :returns: A Key object from this bucket.
        """
        if key_name == '-':
            return Key(self.name, '-', key_type=Key.KEY_STREAM_READABLE)
        else:
            fp = open(key_name, 'rb')
            return Key(self.name, key_name, fp)