react-redux/es/utils/verifyPlainObject.js

Official React bindings for Redux

import isPlainObject from './isPlainObject';
import warning from './warning';
export default function verifyPlainObject(value, displayName, methodName) {
  if (!isPlainObject(value)) {
    warning(`${methodName}() in ${displayName} must return a plain object. Instead received ${value}.`);
  }
}