code: public function valid()
      {
  
          if ($this->container['line1'] === null) {
              return false;
          }
          if (strlen($this->container['line1']) > 200) {
              return false;
          }
          if (strlen($this->container['line2']) > 200) {
              return false;
          }
          if ($this->container['city'] === null) {
              return false;
          }
          if (strlen($this->container['city']) > 50) {
              return false;
          }
          if ($this->container['state'] === null) {
              return false;
          }
          if (strlen($this->container['state']) > 50) {
              return false;
          }
          if ($this->container['postal_code'] === null) {
              return false;
          }
          if (strlen($this->container['postal_code']) > 15) {
              return false;
          }
          if ($this->container['country'] === null) {
              return false;
          }
          if (strlen($this->container['country']) > 2) {
              return false;
          }
          if (strlen($this->container['country']) < 2) {
              return false;
          }
          if (strlen($this->container['first_name']) > 200) {
              return false;
          }
          return true;
      }
docs: validate all the properties in the model
  return true if all passed
  
  @return bool True if all properties are valid