core/src/com/google/inject/util/Types.java
public static ParameterizedType mapOf(Type keyType, Type valueType) {
    return newParameterizedType(Map.class, keyType, valueType);
  }
public static ParameterizedType mapOf(Type keyType, Type valueType) {
    return newParameterizedType(Map.class, keyType, valueType);
  }
Returns a type modelling a {@link Map} whose keys are of type {@code keyType} and whose values
are of type {@code valueType}.

@return a {@link java.io.Serializable serializable} parameterized type.