Function pm#binary_function (?,? -> ?)  function that requires two arguments; currently not specialized by the  SUMO ternary relations since this seems useless (for now)
  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#binary_function_type  class of functions requiring two arguments
  supertype:  pm#ternary_relation__ternaryrelation__ternary_only_relation (?,?,?)  relation with a fixed arity equal to 3; specialized by the SUMO ternary relations not categorized elsewhere
     supertype:  pm#relation_with_particular_property (*)  this rather fuzzy type permits to group categorization schemes less common than those covered by the previous sibling categories
        supertype:  pm#relation__related_thing__relatedthing___related_with (*)  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type

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