Fixed initial function template specialization sequence diagram test case

tests/t20004/t20004.cc

@@ -1,16 +1,49 @@
+#include <string>
+
 namespace clanguml {
 namespace t20004 {
 
 template <typename T> T m4(T p);
 
+template <> [[maybe_unused]] int m4<int>(int p) { return p + 2; }
+
+template <> [[maybe_unused]] unsigned long m4<unsigned long>(unsigned long p)
+{
+    return 1000 * p;
+}
+
 template <typename T> T m3(T p) { return m4<T>(p); }
 
 template <typename T> T m2(T p) { return m3<T>(p); }
 
+template <> [[maybe_unused]] std::string m2<std::string>(std::string p)
+{
+    return std::string{"m2"} + p;
+}
+
 template <typename T> T m1(T p) { return m2<T>(p); }
 
-template <> [[maybe_unused]] int m4<int>(int p) { return p + 2; }
+template <> [[maybe_unused]] float m1<float>(float p) { return 2 * p; }
 
-int main() { return m1<int>(0); }
+template <> [[maybe_unused]] unsigned long m1<unsigned long>(unsigned long p)
+{
+    return m4<unsigned long>(p);
+}
+
+template <> [[maybe_unused]] std::string m1<std::string>(std::string p)
+{
+    return m2<std::string>(p);
+}
+
+int main()
+{
+    m1<float>(2.2);
+
+    m1<unsigned long>(100);
+
+    m1<std::string>("main");
+
+    return m1<int>(0);
+}
 }
 }