code: def validate_data(self):
          
          warnings = {}
          spec_warnings, samp_warnings, site_warnings, loc_warnings = {}, {}, {}, {}
          if self.specimens:
              spec_warnings = self.validate_items(self.specimens, 'specimen')
          if self.samples:
              samp_warnings = self.validate_items(self.samples, 'sample')
          if self.sites:
              site_warnings = self.validate_items(self.sites, 'site')
          if self.locations:
              loc_warnings = self.validate_items(self.locations, 'location')
          return spec_warnings, samp_warnings, site_warnings, loc_warnings
docs: Validate specimen, sample, site, and location data.