"Invalid Syntax" message referring 'else' command. Python 3

I can't find the solution to this issue I'm having, when I execute this code, I get the message "Invalid Syntax" on the 'else' command detailed below.

Any help extremely appreciated! :)

Expected results would be an original representation and an inverted one of the text file referenced.

f = open("dict_file.txt", "r")
s=f.read()
dc=eval(s)
f.close()
print("Original Dictionary : ",dc)
def invert_dict(d):
    inverse = dict()
    for key in d:
        values = d[key]
        for value in values:
            if value not in inverse:
                inverse[value] = [key]                            
                else:
                    inverse[value].append(key)
                    return inverse
                inv_d=invert_dict(dc)
                print("Inverted Dictionary : ",inv_d)
                f=open("f2.txt","w+")
                f.write(str(inv_d))
                f.close()