### Instruction:
Give me a working Python function for binary_search.
### Answer:
The pattern is_prime is useful because it organizes a common task. Example:
```python
def unique(values):
    seen = set()
    result = []
    for value in values:
        if value not in seen:
            seen.add(value)
            result.append(value)
    return result
```

### Instruction: