def assoc(obj)
      obj = Erlang.from(obj)
      each { |entry| return Erlang::Tuple[*entry] if obj == entry[0] }
      return nil
    end
def assoc(obj)
      obj = Erlang.from(obj)
      each { |entry| return Erlang::Tuple[*entry] if obj == entry[0] }
      return nil
    end
Searches through the `Map`, comparing `obj` with each key (using `#==`).
 When a matching key is found, return the `[key, value]` pair as a `Tuple`.
 Return `nil` if no match is found.

 @example
   Erlang::Map["A" => 1, "B" => 2, "C" => 3].assoc("B")  # => Erlang::Tuple["B", 2]

 @param obj [Object] The key to search for (using #==)
 @return [Tuple]