code: def requiredIdr(self,
                      idr: Identifier=None,
                      alias: str=None):
          
  
          # TODO Need to create a new Identifier type that supports DIDs and CIDs
          if idr:
              if ':' in idr:
                  idr = idr.split(':')[1]
          else:
              idr = self.aliasesToIds[alias] if alias else self.defaultId
          if not idr:
              raise EmptyIdentifier
          return idr
docs: Checks whether signer identifier specified, or can it be
          inferred from alias or can be default used instead
  
          :param idr:
          :param alias:
          :param other:
  
          :return: signer identifier