code: def ssn(self, taxpayer_identification_number_type=SSN_TYPE):
          
  
          if taxpayer_identification_number_type == self.ITIN_TYPE:
              return self.itin()
          elif taxpayer_identification_number_type == self.EIN_TYPE:
              return self.ein()
          elif taxpayer_identification_number_type == self.SSN_TYPE:
  
              # Certain numbers are invalid for United States Social Security
              # Numbers. The area (first 3 digits) cannot be 666 or 900-999.
              # The group number (middle digits) cannot be 00. The serial
              # (last 4 digits) cannot be 0000.
  
              area = self.random_int(min=1, max=899)
              if area == 666:
                  area += 1
              group = self.random_int(1, 99)
              serial = self.random_int(1, 9999)
  
              ssn = "{0:03d}-{1:02d}-{2:04d}".format(area, group, serial)
              return ssn
  
          else:
              raise ValueError("taxpayer_identification_number_type must be one of 'SSN', 'EIN', or 'ITIN'.")
docs: Generate a random United States Taxpayer Identification Number of the specified type.
  
          If no type is specified, a US SSN is returned.