Method _match_primaries

lib/sqlalchemy/sql/selectable.py:1408–1417

(
        self,
        left: FromClause,
        right: FromClause,
    )

        self.right._refresh_for_new_column(column)

    def _match_primaries(
        self,
        left: FromClause,
        right: FromClause,
    ) -> ColumnElement[bool]:
        if isinstance(left, Join):
            left_right = left.right
        else:
            left_right = None
        return self._join_condition(left, right, a_subset=left_right)

    @classmethod
    def _join_condition(