def __init__(self, interface, unique=False):
property.__init__(self, self.extension if unique else self.extensions)<EOL>self.interface = interface<EOL>self.__doc__ = ("<STR_LIT>" %<EOL>(self.interface.__module__, self.interface.__name__))<EOL>
Create the extension point.

        :param interface:
          the `Interface` subclass that defines the
          protocol for the extension point.
        :param bool unique:
          If True, then there must be exactly one `Component` implemented
          the specified `Interface` and the property value is the `Component`
          instead of the components list implementing the `Interface`.