message: Fixed fabs() call to build on mac
diff: @@ -317,7 +317,7 @@ std::shared_ptr<Observable> QCMX::getUniqueTerms(
  auto coeff = std::dynamic_pointer_cast<PauliOperator>(term)
  ->begin()
  ->second.coeff();
  - if (std::fabs(coeff) < threshold)
  + if (std::fabs(coeff.real()) < threshold)
  continue;
  uniqueTermsPtr->operator+=(*std::make_shared<PauliOperator>(op));
  }
  