src/Neutrino/HttpClient/Request.php
public function setHeaders($headers, $merge = false)
    {
        $this->header->setHeaders($headers, $merge);

        return $this;
    }
public function setHeaders($headers, $merge = false)
    {
        $this->header->setHeaders($headers, $merge);

        return $this;
    }
Define the headers

@param array $headers
@param bool $merge Merge or Erase current headers

@return $this