code: public function getField(string $fieldId, bool $tryCaseInsensitive = false)
      {
          if (isset($this->fields[$fieldId])) {
              return $this->fields[$fieldId];
          }
  
          if ($tryCaseInsensitive) {
              foreach ($this->fields as $name => $field) {
                  if (\mb_strtolower($name) === \mb_strtolower($fieldId)) {
                      return $field;
                  }
              }
          }
  
          return null;
      }
docs: Returns the field for the passed id.
  
  If the field does not exist, null is returned.
  
  @param string $fieldId
  @param bool   $tryCaseInsensitive
  
  @return Field|null