lib/Assertion.php
function matchFormat(string $format): self {
    return $this->expect($this->target, matches($format));
  }
function matchFormat(string $format): self {
    return $this->expect($this->target, matches($format));
  }
Reports an error if the target does not match the specified format string.
@param string $format The format string to test.
@return self This instance.