def METHOD_NAME(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)