Update hello_world.py

Author: zaihuaji

src/rda_python_template/hello_world.py

@@ -3,10 +3,11 @@
 #
 def main():
 
-   str = "Hello World!"
+   str = get_string('Hua')
    print(str)
-   return str
 
+   def get_string(name):
+      return name + ": Hello World!"
 #
 # call main() to start program
 #