def get_blade_repr(blade_name: str) -> str:
    """Returns the representation to use
    for a given blade.

    Examples:
    - `"12"` -> `"e_12"`
    - `""` -> `"1"`

    Args:
        blade_name: name of the blade in the algebra (eg. `"12"`)

    Returns:
        Representation to use for a given blade
    """
    if blade_name == "":
        return "1"
    return "e_%s" % blade_name