def filter(self, user, operation, resource, iterable):
return iterable<EOL>
Filters an iterable to contain only the items for which the user
is authorized to perform the operation on.

@param[in] user
    The user in question that is being checked.

@param[in] operation
    The operation in question that is being performed (eg. 'read').

@param[in] resource
    The resource instance that is being authorized.

@param[in] iterable
    The iterable of objects to be checked. This method is called
    from the model connector so the actual value of this parameter
    depends on the model connector (eg. it may be a django queryset).

@returns
    Returns an iterable containing the remaining objects.