code: def spectral_density_count(wav, area):
      
      from .binning import calculate_bin_widths, calculate_bin_edges
  
      wav = wav.to(u.AA, equivalencies=u.spectral())
      area = area.to(AREA)
      bin_widths = calculate_bin_widths(calculate_bin_edges(wav))
      factor = bin_widths.value * area.value
  
      def converter_count(x):
          return x * factor
  
      def iconverter_count(x):
          return x / factor
  
      def converter_obmag(x):
          return -2.5 * np.log10(x * factor)
  
      def iconverter_obmag(x):
          return 10**(-0.4 * x) / factor
  
      return [(PHOTLAM, u.count, converter_count, iconverter_count),
              (PHOTLAM, OBMAG, converter_obmag, iconverter_obmag)]
docs: Flux equivalencies between PHOTLAM and count/OBMAG.
  
      Parameters
      ----------
      wav : `~astropy.units.quantity.Quantity`
          Quantity associated with values being converted
          (e.g., wavelength or frequency).
  
      area : `~astropy.units.quantity.Quantity`
          Telescope collecting area.
  
      Returns
      -------
      eqv : list
          List of equivalencies.