code: def resolve(self, other: Type) -> Optional[Type]:
          
          if not isinstance(other, NltkComplexType):
              return None
          if not isinstance(other.second, NltkComplexType):
              return None
          other_first = other.first.resolve(other.second.first)
          if other_first is None:
              return None
          other_first = other_first.resolve(other.second.second)
          if not other_first:
              return None
          other_second = other.second.resolve(ComplexType(other_first, other_first))
          if not other_second:
              return None
          return BinaryOpType(other_first, self._allowed_substitutions, self._signature)
docs: See ``PlaceholderType.resolve``