from typing import SupportsFloat
import math


def _sign(x: SupportsFloat) -> float:
    """Get a 1 with the sign of x.

    Parameters
    ----------
    x : math._SupportsFloatOrIndex
        A number.

    Returns
    -------
    float
        a 1 with the sign of x.
    """
    return math.copysign(1, x)