code: def build_verify_command(self, packages):
          
          if not self.verify_command:
              return None
  
          # The re.match(pkg) used by all_pkgs_by_name_regex() may return
          # an empty list (`[[]]`) when no package matches: avoid building
          # an rpm -V command line with the empty string as the package
          # list in this case.
          by_regex = self.all_pkgs_by_name_regex
          verify_list = filter(None, map(by_regex, packages))
  
          # No packages after regex match?
          if not verify_list:
              return None
  
          verify_packages = ""
          for package_list in verify_list:
              for package in package_list:
                  if any([f in package for f in self.verify_filter]):
                      continue
                  if len(verify_packages):
                      verify_packages += " "
                  verify_packages += package
          return self.verify_command + " " + verify_packages
docs: build_verify_command(self, packages) -> str
              Generate a command to verify the list of packages given
              in ``packages`` using the native package manager's
              verification tool.
  
              The command to be executed is returned as a string that
              may be passed to a command execution routine (for e.g.
              ``sos_get_command_output()``.
  
              :param packages: a string, or a list of strings giving
                               package names to be verified.
              :returns: a string containing an executable command
                        that will perform verification of the given
                        packages.
              :returntype: str or ``NoneType``