Type of the `filter' argument to traversal functions

[Anton Shepelev <anton.txt-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Hello, all

I  am  trying to write a Lua filter.  The documenta-
tion to walk_block() and walk_filter()  states  that
the  second  parameter  is  "a  Lua filter (table of
functions) to be applied within the block  element".
When, however, I pass a filter table consisting of a
single row:

   pandoc.walk_block( elem, {{ Span = OnSpan }} )

it is ignored. By experiment I found that the  func-
tions  expect not a table of functions, but a single
row of it:

   pandoc.walk_block( elem, { Span = OnSpan } )

Now it works. Is the documentation incorrect or do I
misinterpret  it?  For aught I know, {Span = OnSpan}
is not a "table of functions".

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