code: def check_residues(self):
          '''Checks to make sure that each atom type is unique per residue.'''
          for chain, residue_ids in self.residues.iteritems():
              for residue_id, residue in residue_ids.iteritems():
                  for record_type, atoms in residue.records.iteritems():
                      freq = {}
                      for atom in atoms:
                          rec_id = atom.name + atom.conformation
                          freq[rec_id] = freq.get(rec_id, 0)
                          freq[rec_id] += 1
                      for atom_type, count in freq.items():
                          if count > 1:
                              raise Exception('{0} occurrences of atom type {1} for record type {2} occur in residue {3} in chain {4}.'.format(count, atom_type, record_type, residue_id.strip(), chain)f check_residues(self):
          '''Checks to make sure that each atom type is unique per residue.'''
          for chain, residue_ids in self.residues.iteritems():
              for residue_id, residue in residue_ids.iteritems():
                  for record_type, atoms in residue.records.iteritems():
                      freq = {}
                      for atom in atoms:
                          rec_id = atom.name + atom.conformation
                          freq[rec_id] = freq.get(rec_id, 0)
                          freq[rec_id] += 1
                      for atom_type, count in freq.items():
                          if count > 1:
                              raise Exception('{0} occurrences of atom type {1} for record type {2} occur in residue {3} in chain {4}.'.format(count, atom_type, record_type, residue_id.strip(), chain))
docs: Checks to make sure that each atom type is unique per residue.