MutateInSpec.CasPlaceholder won't work because value arg is JSON.stringify-d

static _create(opType, path, value, options) {

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if (value ===CasPlaceholder ) {

This will always return false, because in the call to _create, 'value' is always JSON.stringify-d.  

CasPlaceholder is not a string.  Also JSON.stringify(CasPlaceholder) is 'undefined'

  static replace(path, value, options)

{     return this._create(       binding.LCBX_SDCMD_REPLACE, path, JSON.stringify(value), options);   }