Return Python list of (spanner, index) pairs. Each (spanner, index) pair gives a spanner which dominates all components in ‘components’ together with the start-index at which spanner first encounters ‘components’.
Use this helper to ‘lift’ any and all spanners temporarily from ‘components’, perform some action to the underlying score tree, and then reattach all spanners to new score components.
This operation always leaves all expressions in tact.