String Concatenation

[durgadarba97]

Error :
line 63, in evaluate
return int(self.expLeft.evaluate()) + int(self.expRight.evaluate())
ValueError: invalid literal for int() with base 10: 'hello'

Input :
hello = "hello" + "world"

print(hello)

I should check the type when doing addition. I could also implement a subtract feature that removes all instances of a token. For example,
"Hello" + "World" = "Hello World"
"Hello World" - "World" = "Hello"
"Hello World" - "o" = "Hell Wrld"