please do not use python modules, only built in data types and functions, thank you

3. camel_case (var_name) It takes a string as a parameter, var_name, that represents a variable name with underscores separating words and returns the variable name in camel case. If var name consists only of underscores, then an empty string should be returned. camel_case ("to_ca-el_case") 'toCamelCase' camel_case("t0_cAMeL_CaSe") 'toCamelCase' camel_case("_TO_CAMEL__C_CASE") 'toCamelCase' camel_case("__.")