code: func (msp *bccspmsp) GetDefaultSigningIdentity() (SigningIdentity, error) {
  	mspLogger.Debugf("Obtaining default signing identity")
  
  	if msp.signer == nil {
  		return nil, errors.New("this MSP does not possess a valid default signing identity")
  	}
  
  	return msp.signer, nil
  }
docs: // GetDefaultSigningIdentity returns the
  // default signing identity for this MSP (if any)