@mui/system/esm/preprocessStyles.js

MUI System is a set of CSS utilities to help you build custom designs more efficiently. It makes it possible to rapidly lay out custom designs.

import { internal_serializeStyles } from '@mui/styled-engine';
export default function preprocessStyles(input) {
  const {
    variants,
    ...style
  } = input;
  const result = {
    variants,
    style: internal_serializeStyles(style),
    isProcessed: true
  };

  // Not supported on styled-components
  if (result.style === style) {
    return result;
  }
  if (variants) {
    variants.forEach(variant => {
      if (typeof variant.style !== 'function') {
        variant.style = internal_serializeStyles(variant.style);
      }
    });
  }
  return result;
}