text: #ifndef STAN_MATH_PRIM_FUN_IMAG_HPP
  #define STAN_MATH_PRIM_FUN_IMAG_HPP
  
  #include <stan/math/prim/meta.hpp>
  #include <complex>
  
  namespace stan {
  namespace math {
  
  /**
   * Return the imaginary part of the complex argument.
   *
   * @tparam T value type of argument
   * @param[in] z argument
   * @return imaginary part of argument
   */
  template <typename T, require_autodiff_t<T>>
  T imag(const std::complex<T>& z) {
    return z.imag();
  }
  
  }  // namespace math
  }  // namespace stan
  
  #endif
  