code: def _set_virtualbox(self):
          
          '''
              a method to set virtualbox environment variables for docker-machine
              
          :return: True
          '''
  
          from os import environ
          if not environ.get('DOCKER_CERT_PATH'):
              import re
              sys_command = 'docker-machine env %s' % self.vbox
              cmd_output = self.command(sys_command)
              variable_list = ['DOCKER_TLS_VERIFY', 'DOCKER_HOST', 'DOCKER_CERT_PATH', 'DOCKER_MACHINE_NAME']
              for variable in variable_list:
                  env_start = '%s="' % variable
                  env_end = '"\\n'
                  env_regex = '%s.*?%s' % (env_start, env_end)
                  env_pattern = re.compile(env_regex)
                  env_statement = env_pattern.findall(cmd_output)
                  env_var = env_statement[0].replace(env_start, '').replace('"\n', '')
                  environ[variable] = env_var
  
          return Truf _set_virtualbox(self):
          
          '''
              a method to set virtualbox environment variables for docker-machine
              
          :return: True
          '''
  
          from os import environ
          if not environ.get('DOCKER_CERT_PATH'):
              import re
              sys_command = 'docker-machine env %s' % self.vbox
              cmd_output = self.command(sys_command)
              variable_list = ['DOCKER_TLS_VERIFY', 'DOCKER_HOST', 'DOCKER_CERT_PATH', 'DOCKER_MACHINE_NAME']
              for variable in variable_list:
                  env_start = '%s="' % variable
                  env_end = '"\\n'
                  env_regex = '%s.*?%s' % (env_start, env_end)
                  env_pattern = re.compile(env_regex)
                  env_statement = env_pattern.findall(cmd_output)
                  env_var = env_statement[0].replace(env_start, '').replace('"\n', '')
                  environ[variable] = env_var
  
          return True
docs: a method to set virtualbox environment variables for docker-machine
              
          :return: True