Return a json dictionary representing this model.

def _to_dict(self):
        """Return a json dictionary representing this model."""
        _dict = {}
        if hasattr(self, 'environment_id') and self.environment_id is not None:
            _dict['environment_id'] = self.environment_id
        if hasattr(self, 'name') and self.name is not None:
            _dict['name'] = self.name
        if hasattr(self, 'description') and self.description is not None:
            _dict['description'] = self.description
        if hasattr(self, 'created') and self.created is not None:
            _dict['created'] = datetime_to_string(self.created)
        if hasattr(self, 'updated') and self.updated is not None:
            _dict['updated'] = datetime_to_string(self.updated)
        if hasattr(self, 'status') and self.status is not None:
            _dict['status'] = self.status
        if hasattr(self, 'read_only') and self.read_only is not None:
            _dict['read_only'] = self.read_only
        if hasattr(self, 'size') and self.size is not None:
            _dict['size'] = self.size
        if hasattr(self, 'requested_size') and self.requested_size is not None:
            _dict['requested_size'] = self.requested_size
        if hasattr(self, 'index_capacity') and self.index_capacity is not None:
            _dict['index_capacity'] = self.index_capacity._to_dict()
        if hasattr(self, 'search_status') and self.search_status is not None:
            _dict['search_status'] = self.search_status._to_dict()
        return _dict