function removeSchema(schemaKeyRef) {
  if (schemaKeyRef instanceof RegExp) {
    _removeAllSchemas(this, this._schemas, schemaKeyRef);
    _removeAllSchemas(this, this._refs, schemaKeyRef);
    return;
  }
  switch (typeof schemaKeyRef) {
    case 'undefined':
      _removeAllSchemas(this, this._schemas);
      _removeAllSchemas(this, this._refs);
      this._cache.clear();
      return;
    case 'string':
      var schemaObj = _getSchemaObj(this, schemaKeyRef);
      if (schemaObj) this._cache.del(schemaObj.cacheKey);
      delete this._schemas[schemaKeyRef];
      delete this._refs[schemaKeyRef];
      return;
    case 'object':
      var serialize = this._opts.serialize;
      var cacheKey = serialize ? serialize(schemaKeyRef) : schemaKeyRef;
      this._cache.del(cacheKey);
      var id = this._getId(schemaKeyRef);
      if (id) {
        id = resolve.normalizeId(id);
        delete this._schemas[id];
        delete this._refs[id];
      }
  }
}
Remove cached schema(s).
If no parameter is passed all schemas but meta-schemas are removed.
If RegExp is passed all schemas with key/id matching pattern but meta-schemas are removed.
Even if schema is referenced by other schemas it still can be removed as other schemas have local references.
@this   Ajv
@param  {String|Object|RegExp} schemaKeyRef key, ref, pattern to match key/ref or schema object