code: def add_specimen(self, spec_name, samp_name=None, er_data=None, pmag_data=None):
          
          if samp_name:
              sample = self.find_by_name(samp_name, self.samples)
              if not sample:
                  print("""-W- {} is not a currently existing sample.
  Creating a new sample named: {} """.format(samp_name, samp_name))
                  sample = self.add_sample(samp_name)
          else:
              sample = None
  
          specimen = Specimen(spec_name, sample, self.data_model, er_data, pmag_data)
  
          self.specimens.append(specimen)
          if sample:
              sample.specimens.append(specimen)
          return specimen
docs: Create a Specimen object and add it to self.specimens.
          If a sample name is provided, add the specimen to sample.specimens as well.