Although there exist many naming conventions in computer programming, two of them are particularly widespread. In the first, words in a variable name are separated using underscores. In the second, words in a variable name are written in mixed case, and are strung together without a delimiter. By mixed case, we mean that the first word is written in lowercase, and that subsequent words have a capital first letter. Write a function to_mixed_case(name) that converts a variable name from the former convention to the latter. Leading and trailing underscores should be ignored. If the variable name consists solely of underscores, then an empty string should be returned.