How to use the @uifabric/merge-styles.mergeStyleSets function in @uifabric/merge-styles

const selectors: any                                                                                  = {};
            selectors[`> *:nth-child(-n+${this.headerCount})`]                                                    = {
                borderBottom: "1px solid rgba(0, 0, 0, 0.35)"
            };
            selectors[`> *:not(:nth-last-child(-n+${this.headerCount})):not(:nth-child(-n+${this.headerCount}))`] = {
                borderBottom: "1px solid rgba(0, 0, 0, 0.2)"
            };
            selectors[`> *:not(:nth-child(${this.headerCount}n))`]                                                = {
                borderRight: "1px solid rgba(0, 0, 0, 0.2)"
            };
            selectors[`> *`]                                                                                      = {
                paddingLeft: "5px"
            };

            // noinspection TypeScriptValidateTypes
            return mergeStyleSets({
                root: [
                    "technical-description",
                    {
                        gridTemplateColumns: "200px ".repeat(this.headerCount - 1) + "auto",
                        display:             "grid",
                        selectors
                    },
                ]
            });
        }
    }

private get classNames() {
            return mergeStyleSets(getStyles({
                theme: loadTheme({}),
                isButton: !this.href,
                isDisabled: this.disabled
            }));
        }
    }

public get classNames() : IOfficeOverlayStyles {
            return mergeStyleSets(getStyles({
                isDark: this.isDarkThemed,
                isNone: !this.visible,
                theme: createTheme({}),
            }));
        }

private get classNames() {
            return mergeStyleSets(getStyles({
                className: "",
                disabled: this.disabled,
                required: this.required,
                theme: loadTheme({})
            }));
        }
    }

return (getStyles?: IStyleFunctionOrObject, styleProps?: TStyleProps): IClassNames =>
    mergeStyleSets(getStyles && (typeof getStyles === 'function' ? getStyles(styleProps!) : getStyles));
}

private get classNames() {
            return mergeStyleSets(getStyles({
                theme: loadTheme({}),
                vertical: this.vertical,
                disabled: this.disabled,
                showValue: this.showValue,
                showTransitions: this.renderedValue === this.internalValue
            }));
        }

private get classNames() {
            return mergeStyleSets(getStyles({
                checked:                  this.isChecked,
                disabled:                 this.disabled,
                className:                "",
                isUsingCustomLabelRender: false,
                theme:                    loadTheme({})
            }));
        }
    }

private get classNames() {
            const {iconClassName, children} = this.getIconContent(this.iconName);
            this.children = children;
            return mergeStyleSets(getStyles({
                iconClassName,
                className: "",
                isImage: this.isImage,
                isPlaceholder: typeof this.iconName === "string" && this.iconName.length === 0,
                styles: {}
            }));
        }

private get classNames() {
            return mergeStyleSets(getStyles({
                theme: loadTheme({}),
                labelPosition: this.labelPosition,
                size: this.size
            }));
        }
    }

private get classNames() {
            return mergeStyleSets(getStyles({
                theme: loadTheme({}),
                checked: this.checked,
                disabled: this.disabled
            }));
        }