code: def setup_keys(self):
          
  
          discovery_methods = {}
          discovery_years = {}
          nan_list = []
  
          # Initial Loop to get keys
          for planet in self.planet_list:
              if 'Solar System' in planet.params['list'] and self.skip_solar_system_planets:
                  continue
              try:
                  discovery_methods[planet.discoveryMethod] += 1
              except KeyError:
                  discovery_methods[planet.discoveryMethod] = 1
  
              try:
                  discovery_years[planet.discoveryYear] += 1
              except KeyError:
                  discovery_years[planet.discoveryYear] = 1
  
              if planet.discoveryMethod is np.nan:
                  nan_list.append(planet)
  
          self.nan_list = nan_list
  
          return discovery_years
docs: Build the initial data dictionary to store the values