class_docstr: ReverseType is a kind of ``PlaceholderType`` where type resolution involves matching the return
  type with the reverse of the argument type. So all we care about are the types of the surrounding
  expressions, and return a resolution that matches whatever parts are present in the type signatures
  of the arguments and the return expressions.
  
  Following are the resolutions for some example type signatures being matched against::
  
      <?, <e,r>>      :   <<r,e>, <e,r>>
      <<r,?>, <e,?>>  :   <<r,e>, <e,r>>
      <<r,?>, ?>      :   <<r,?>, <?,r>>>
      <<r,?>, <?,e>>  :   None
code: def resolve(self, other):
      # Idea: Since its signature is <<#1,#2>,<#2,#1>> no information about types in self is
      # relevant.  All that matters is that other.first resolves against the reverse of
      # other.second and vice versa.
      if not isinstance(other, NltkComplexType):
          return None
      # other.first and other.second are the argument and return types respectively.
      reversed_second = ComplexType(
          other.second.second, other.second.first
      )
      other_first = other.first.resolve(reversed_second)
      if not other_first:
          return None
      reversed_first = ComplexType(
          other_first.second, other_first.first
      )
      other_second = other.second.resolve(reversed_first)
      if not other_second:
          return None
      return ReverseType(other_first, other_second)
  
imports: from __future__ import absolute_import
  from nltk.sem.logic import Type, BasicType, ANY_TYPE, ComplexType
  from allennlp.semparse.type_declarations.type_declaration import ComplexType, HigherOrderType
  from allennlp.semparse.type_declarations.type_declaration import PlaceholderType, NamedBasicType
  from allennlp.semparse.type_declarations.type_declaration import UnaryOpType, BinaryOpType
label_desc: Use image node_id 2 for calling the ReverseType obj's underlying member method code with example usage: obj.resolve(other) and returns: ReverseType, None, None, None