def http_multipart_post(path, parts, parameters={}, headers={})
      with_encoded_path_and_checked_response(path, parameters) do |encoded_path|
        https_request.request(Net::HTTP::Post::Multipart.new(encoded_path, parts, {"Authorization" => "OAuth #{self.oauth_token}"}.merge(headers)))
      end
    end
def http_multipart_post(path, parts, parameters={}, headers={})
      with_encoded_path_and_checked_response(path, parameters) do |encoded_path|
        https_request.request(Net::HTTP::Post::Multipart.new(encoded_path, parts, {"Authorization" => "OAuth #{self.oauth_token}"}.merge(headers)))
      end
    end
Performs an HTTP POST request to the specified path (relative to self.instance_url), using Content-Type multiplart/form-data.
 The parts of the body of the request are taken from parts_. Query parameters are included from _parameters_.  The required
 +Authorization+ header is automatically included, as are any additional headers specified in _headers_.
 Returns the HTTPResult if it is of type HTTPSuccess- raises SalesForceError otherwise.