, because <code><a href="../reference/sum_byname.html">sum_byname()</a></code> is
ambiguous for a data frame. Should the column be returned unchanged,
because each element is interpreted as the augend for a series of sums
that is missing addends, in which case the length of the returned object
is the same as the length of the input? Or should the list of objects be
summed down the column, returning only a single item (for each group),
as in the <code><a href="https://dplyr.tidyverse.org/reference/summarise.