Question about the code: function File:get_node_at_cursor(cursor)

[Maltimore]

This is in the file lua/orgmode/parser/file.lua. I can't figure out why in the code below in the third line, the cursor range is set to cursor[1] -1. Why the -1? At first I thought that maybe self.tree:root():named_descendant_for_range() is 0-indexed but then it doesn't make sense that the cursor[2] is not decreased by 1.

function File:get_node_at_cursor(cursor)
  cursor = cursor or vim.api.nvim_win_get_cursor(0)
  local cursor_range = { cursor[1] - 1 , cursor[2] }
  -- Parsing a node from the last empty line in a file causes failure with parsing
  -- because the line doesn't properly belong to any node.
  -- In that case we go only 1 line up to get the proper context
  if (cursor_range[1] + 1) == vim.fn.line('$') and vim.trim(vim.fn.getline('$')) == '' then
    cursor_range[1] = cursor_range[1] - 1
  end
  return self.tree:root():named_descendant_for_range(cursor_range[1], cursor_range[2], cursor_range[1], cursor_range[2])
end

[jgollenz]

From :h nvim_win_get_cursor():

nvim_win_get_cursor({window})                          *nvim_win_get_cursor()*
    Gets the (1,0)-indexed, buffer-relative cursor position for a given window
    (different windows showing the same buffer have independent cursor
    positions). |api-indexing|

    Parameters:  
      • {window}  Window handle, or 0 for current window

    Return:  
        (row, col) tuple

cursor[2] is already 0-indexed, but cursor[1] is not.

[Maltimore]

Ah, thanks a lot!
I should've checked the help myself but I guess it didn't occur to me that within the same program, the same function even, people would use both 0- and 1-based indexing!