You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: CarlosEduardoL.rs
    path of file: ./repos/retos-programacion-2023/Retos/Reto #9 - HETEROGRAMA, ISOGRAMA Y PANGRAMA [Fácil]/rust
    
    the code of the file until where you have to start completion: use std::collections::HashSet;

/// Returns true if the given word is a heterogram (i.e., contains no repeated letters), false otherwise.
fn is_heterogram(word: &str) -> bool {
    let mut unique_letters = HashSet::new();
    for
    
fn is_isogram(word: &str) -> bool {
    let mut counts = [0; 26];
    for c in word.chars() {
        if c.is_alphabetic() {
            let index = c.to_ascii_lowercase() as usize - 'a' as usize;
            counts[index] += 1;
        }
    }
    let mut first_count = 0;
    for count in counts.iter() {
        if *count != 0 {
            if first_count == 0 {
                first_count = *count;
            } else if *count != first_count {
                return false;
            }
        }
    }
    true
}