title: error in sign-in at Create Transaction blockcypher/php-client
body: <p>here my code for create and sign and send</p>
  
  <pre><code>  $request = clone $tx;
  /// For Sample Purposes Only.
      $params = array(
             'includeToSignTx' =&gt; 1,
             'script_type'=&gt;'mutlisig-n-of-m',
          );
  $txClient = new TXClient($apiContext);
  
  try {
  
    // dd($tx);
      $txSkeleton = $txClient-&gt;create($tx,$params);
      $privateKeys = array("private key");
  $txSkeleton = $txClient-&gt;sign($txSkeleton, $privateKeys);
  $txSkeleton = $txClient-&gt;send($txSkeleton);
  } catch (Exception $ex) {
      dd("Created TX", "TXSkeleton", null, $request, $ex);
      exit(1);
  }
  </code></pre>
  
  <p>This is the error i got:</p>
  
  <blockquote>
    <p>FatalThrowableError in PrivateKeyList.php line 54: Type error:
    Argument 1 passed to
    BlockCypher\Crypto\PrivateKeyList::addPrivateKey() must be an instance
    of BitWasp\Bitcoin\Key\PrivateKeyInterface, instance of
    BitWasp\Bitcoin\Crypto\EcAdapter\Impl\PhpEcc\Key\PrivateKey given,
    called in
    /home/pixel/Documents/tests/vendor/blockcypher/php-client/lib/BlockCypher/Crypto/PrivateKeyList.php
    on line 43</p>
  </blockquote>
  
  <p>here is code</p>
  
  <pre><code>public function addPrivateKey(PrivateKeyInterface $privateKey)
  {
     $pubKeyHex = $privateKey-&gt;getPublicKey()-&gt;getHex();
     $this-&gt;privateKeys[$pubKeyHex] = $privateKey;
  }
  </code></pre>