def __init__(self, items = None, version = None):
if items is not None:<EOL><INDENT>self._items = list(items)<EOL><DEDENT>else:<EOL><INDENT>self._items = []<EOL><DEDENT>self.version = version<EOL>
:Parameters:
    - `items`: sequence of roster items
    - `version`: optional roster version string
:Types:
    - `items`: iterable
    - `version`: `unicode`