_expandSelectionOnSign() {
        const [signPosition, currencySymbolPosition] = this._getSignPosition();
        const selection = this.selection;

        // If selection catches something except sign and catches only space from sign
        if (selection.start < currencySymbolPosition && selection.end > signPosition) {
            // Then select without empty space
            if ((selection.start < signPosition || selection.end > currencySymbolPosition) &&
                AutoNumericHelper.getElementValue(this.domElement).substring(Math.max(selection.start, signPosition), Math.min(selection.end, currencySymbolPosition))
                    .match(/^\s*$/)) {
                if (selection.start < signPosition) {
                    this._setSelection(selection.start, signPosition);
                } else {
                    this._setSelection(currencySymbolPosition, selection.end);
                }
            } else {
                // Else select with whole sign
                this._setSelection(Math.min(selection.start, signPosition), Math.max(selection.end, currencySymbolPosition));
            }
        }
    }
Expands selection to cover whole sign
Prevents partial deletion/copying/overwriting of a sign
@private