These printing filters are defined when one of the standard sets of rules (poly.rules or float.rules) is used.

dense( SECTION )
Takes each row of a sparse matrix with (implicit) 0/1 entries and extends it to a dense vector. Useful for VERTICES_IN_FACETS, GRAPH, or DUAL_GRAPH.
labeled( DATA_SECTION, LABELS_SECTION )
The first argument is a data section, which is expected to contain sets of cardinals, and the second one is a section with textual labels. In the output, each cardinal number will be substituted by the label with corresponding index; the indices start, as usual, with 0.
numbered( DATA_SECTION )
Equivalent to row_labeled with omitted second argument. Preserved for backwards compatibility.
packed( SECTION )
In each data line, sorts the elements, counts the number of their occurence and prints the line in the form "ELEMENT*COUNT ...". Useful for VERTEX_DEGREES and similar sections.
row_labeled( DATA_SECTION [, LABELS_SECTION ] )
The first argument is a data section, and the second (optional) one is a section with textual labels. In the output, each line (or each word, if the data consists of a single line,) is prepended by the corresponding label and a colon. If the second argument is omitted, ordinal numbers starting with 0 are taken instead.