Function useOpacity

useOpacity(
    keys: string[],
): {
    handleMouseEnter: (__namedParameters: any) => void;
    handleMouseLeave: () => void;
    handlePayloadUniqBy: (payload: Payload) => Payload;
    opacities: Record<string, number>;
    selectedKey: string | null;
}
Handles reducing opacities when keys are hovered over in a legend. Meant to be used with a Legend component.
Parameters
- keys: string[]
  keys appearing in a legend
Returns {
    handleMouseEnter: (__namedParameters: any) => void;
    handleMouseLeave: () => void;
    handlePayloadUniqBy: (payload: Payload) => Payload;
    opacities: Record<string, number>;
    selectedKey: string | null;
}
Example
```
const {
    opacities,
    handleMouseEnter,
    handleMouseLeave,
    handlePayloadUniqBy,
} = useOpacity(keys);

const lines = keys.map((dataKey) =>
    <Line dataKey={dataKey} opacity={opacities[dataKey]}/>
);

<Legend
    onMouseEnter={handleMouseEnter}
    onMouseLeave={handleMouseLeave}
    payloadUniqBy={handlePayloadUniqBy}
/>
```