Incorporating methods into data types enhances code reusability, but challenges arise when unnecessary parameters, such as a filename, complicate the interface. A common issue occurs when the function requires a filename, even when it may not be needed, leading to awkward conditional checks for empty inputs. A more elegant solution involves using variadic parameters, allowing the function to accept a flexible number of input strings, including none at all. This simplifies the code by transforming the filename parameter into a slice of strings, enabling seamless handling of zero or more filenames without compromising the function's usability. This approach not only streamlines the code but also maintains clean, user-friendly interfaces, paving the way for further enhancements, such as combining counts in future lessons.