docs: public static SpreadMap toSpreadMap(List self) {
          if (self == null)
              throw new GroovyRuntimeException("Fail to convert List to SpreadMap, because it is null.");
          else if (self.size() % 2 != 0)
              throw new GroovyRuntimeException("Fail to convert List to SpreadMap, because it's size is not even.");
          else
              return new SpreadMap(self);
      }