How to style a Material Ui component

Question

I am trying to apply a condition margin to a component. This function receive prop. When the prop.children has a value I want to change the margin. I marked the section I have issues with with //issue here

const StyledTreeItem = styled((props) => (
  <TreeItem {...props} TransitionComponent={TransitionComponent} />
))(({ theme }) => ({
  [`& .${treeItemClasses.iconContainer}`]: {
    "& .close": {
      opacity: 0.3,
    },
  },
  [`& .${treeItemClasses.group}`]: {
    marginLeft: 15,
    paddingLeft: 18,
    borderLeft: `1px dashed ${alpha(theme.palette.text.primary, 0.4)}`,
  },
  [`& .${treeItemClasses.label}`]: {
    // issue here
    marginLeft: props.children.length > 0 && 14,
  },
}));