In python, mypy will erroneously annotate a list comprehension operating on e.g. three inputs as returning an unknown number of values, when of course it should be returning exactly three values. How can this mypy annotation be fixed?
When using list comprehensions in Python, `mypy` can sometimes infer the return type incorrectly, especially if the comprehension is complex or operates on multiple inputs. To ensure that `mypy` understands that your list comprehension is returning a specific number of values, you can use a few strategies.

### Strategies to Fix Mypy Annotations

1. **Explicit Type Annotations**: Provide explicit type annotations for the variables involved in the comprehension. This helps `mypy` understand the types being used.

2. **Use Tuples**: If the list comprehension is intended to create tuples of fixed sizes, you can create tuples directly instead of lists. This gives `mypy` a clearer indication of the expected return type.

3. **Type Aliases**: You can define a type alias to represent the expected output type, which can be helpful for clarity.

### Example

Here's an example that demonstrates these strategies:

```python
from typing import List, Tuple

# Define a type alias for clarity
ValueTuple = Tuple[int, int, int]

def process_data(inputs: List[int]) -> List[ValueTuple]:
    return [(x, x**2, x**3) for x in inputs]

# Example usage
result = process_data([1, 2, 3])
print(result)  # Output: [(1, 1, 1), (2, 4, 8), (3, 9, 27)]
```

### Explanation
 Mypy is a static type checker for Python, and it can sometimes have difficulty inferring the correct types, especially in complex expressions like list comprehensions operating on multiple inputs. However, you can help mypy by providing explicit type annotations.

To annotate a list comprehension that operates on multiple inputs and returns a list of a specific type, you can use the `List` type from the `typing` module. Here's an example:
```python
from typing import List

def process_three_inputs(a: int, b: int, c: int) -> List[int]:
    return [x + y + z for x in [a] for y in [b] for z in [c]]
```
In this example, the `process_three_inputs` function takes three `int` arguments and returns a `List` of `int` values. The list comprehension inside the function adds together the three inputs (`x`, `y`, and `z`) for each combination of values from the input lists.

By providing an explicit type annotation for the function return type, you can help mypy understand that the list comprehension returns a list of three integers, rather than an unknown number of values.

If you want to annotate a list comprehension that returns a list of a custom class, you can define the class and use its name