28def downgrade():
   29    if op.get_context().bind.dialect.name == 'mssql':
   30        op.drop_constraint('ck_ps_systems_follow_early_media_fork_yesno_values','ps_systems')
   31        op.drop_constraint('ck_ps_systems_accept_multiple_sdp_answers_yesno_values','ps_systems')
   32        op.drop_constraint('ck_ps_endpoints_follow_early_media_fork_yesno_values','ps_endpoints')
   33        op.drop_constraint('ck_ps_endpoints_accept_multiple_sdp_answers_yesno_values','ps_endpoints')
   34    op.drop_column('ps_systems', 'follow_early_media_fork')
   35    op.drop_column('ps_systems', 'accept_multiple_sdp_answers')
   36    op.drop_column('ps_endpoints', 'follow_early_media_fork')
   37    op.drop_column('ps_endpoints', 'accept_multiple_sdp_answers')