function warnIfInvalidElement(Component, element) {
  if (process.env.NODE_ENV !== 'production') {
    process.env.NODE_ENV !== 'production' ? warning(element === null || element === false || React.isValidElement(element), '%s(...): A valid React element (or null) must be returned. You may have ' + 'returned undefined, an array or some other invalid object.', Component.displayName || Component.name || 'Component') : void 0;
    process.env.NODE_ENV !== 'production' ? warning(!Component.childContextTypes, '%s(...): childContextTypes cannot be defined on a functional component.', Component.displayName || Component.name || 'Component') : void 0;
  }
}
Initializes the component, renders markup, and registers event listeners.

@param {ReactReconcileTransaction|ReactServerRenderingTransaction} transaction
@param {?object} hostParent
@param {?object} hostContainerInfo
@param {?object} context
@return {?string} Rendered markup to be inserted into the DOM.
@final
@internal