Function sumo#list_fn (* -> sumo#list)  a function that takes any number of arguments and returns the list containing those arguments in exactly the same order
  type:  pm#function_type  term-forming relation that maps from a n-tuple of arguments to a range and that associates this n-tuple with at most one range element; note that the range is a set_or_class, and each element of the range is an instance of the set_or_class
  type:  pm#total_valued_relation_type  when there exists an assignment for the last argument position of the relation given any assignment of values to every argument position except the last one; note that declaring a relation to be both a total_valued_relation and a single_valued_relation means that it is a total function
  type:  pm#variable_arity_relation_type  class of relations that do not have a fixed number of arguments
  supertype:  pm#relation_to_collection (*,pm#collection)
     supertype:  pm#relation_from/to_thing_of_common_kind (*)  this type permits to categorize relations according to their signatures and hence offers (i) a concise way to set essential exclusion relations, and (ii) a systematic and easy-to-follow categorization
        >part of:  pm#relation__related_thing__relatedthing___related_with  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type
     supertype:  pm#what_relation (*)
        supertype:  pm#wh-/how_relation (*)  this type permits to categorize relations according to the usual who/what/why/where/when/how questions ; this is a traditional but very subjective and ineffective way of categorizing relations 
           >part of:  pm#relation__related_thing__relatedthing___related_with  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type