"""
One-line summary of the transformer's purpose and when to use it.

Args:
    param (type): What it does and expected values.
    param2 (type, optional): Purpose. Defaults to X.

Raises:
    ValueError: When X condition occurs.

Example:
    ```python
    # Most common usage pattern
    Transformer(param="value")

    # In pipeline context
    VariantPipe().then(Transformer(param="value")).then(Build())
    ```

Note:
    Key limitation or gotcha users must know.
"""
