func (s *NotesService) ListSnippetNotes(pid interface{}, snippet int, options ...OptionFunc) ([]*Note, *Response, error) {
	project, err := parseID(pid)
	if err != nil {
		return nil, nil, err
	}
	u := fmt.Sprintf("projects/%s/snippets/%d/notes", url.QueryEscape(project), snippet)
	req, err := s.client.NewRequest("GET", u, nil, options)
	if err != nil {
		return nil, nil, err
	}
	var n []*Note
	resp, err := s.client.Do(req, &n)
	if err != nil {
		return nil, resp, err
	}
	return n, resp, err
}
ListSnippetNotes gets a list of all notes for a single snippet. Snippet
notes are comments users can post to a snippet.

GitLab API docs:
https://docs.gitlab.com/ce/api/notes.html#list-all-snippet-notes
package gitlab
import (
	"fmt"
	"net/url"
	"time"
)
type NotesService struct {
	client *Client
}
type Note struct {
	ID         int    `json:"id"`
	Body       string `json:"body"`
	Attachment string `json:"attachment"`
	Title      string `json:"title"`
	FileName   string `json:"file_name"`
	Author     struct {
		ID        int        `json:"id"`
		Username  string     `json:"username"`
		Email     string     `json:"email"`
		Name      string     `json:"name"`
		State     string     `json:"state"`
		CreatedAt *time.Time `json:"created_at"`
	} `json:"author"`
	System    bool       `json:"system"`
	ExpiresAt *time.Time `json:"expires_at"`
	UpdatedAt *time.Time `json:"updated_at"`
	CreatedAt *time.Time `json:"created_at"`
}
func (n Note) String() string {
	return Stringify(n)
}
type ListIssueNotesOptions struct {
	ListOptions
}
func (s *NotesService) ListIssueNotes(pid interface{}, issue int, opt *ListIssueNotesOptions, options ...OptionFunc) ([]*Note, *Response, error) {
	project, err := parseID(pid)
	if err != nil {
		return nil, nil, err
	}
	u := fmt.Sprintf("projects/%s/issues/%d/notes", url.QueryEscape(project), issue)
	req, err := s.client.NewRequest("GET", u, opt, options)
	if err != nil {
		return nil, nil, err
	}
	var n []*Note
	resp, err := s.client.Do(req, &n)
	if err != nil {
		return nil, resp, err
	}
	return n, resp, err
}
func (s *NotesService) GetIssueNote(pid interface{}, issue, note int, options ...OptionFunc) (*Note, *Response, error) {
	project, err := parseID(pid)
	if err != nil {
		return nil, nil, err
	}
	u := fmt.Sprintf("projects/%s/issues/%d/notes/%d", url.QueryEscape(project), issue, note)
	req, err := s.client.NewRequest("GET", u, nil, options)
	if err != nil {
		return nil, nil, err
	}
	n := new(Note)
	resp, err := s.client.Do(req, n)
	if err != nil {
		return nil, resp, err
	}
	return n, resp, err
}
type CreateIssueNoteOptions struct {
	Body *string `url:"body,omitempty" json:"body,omitempty"`
}
func (s *NotesService) CreateIssueNote(pid interface{}, issue int, opt *CreateIssueNoteOptions, options ...OptionFunc) (*Note, *Response, error) {
	project, err := parseID(pid)
	if err != nil {
		return nil, nil, err
	}
	u := fmt.Sprintf("projects/%s/issues/%d/notes", url.QueryEscape(project), issue)
	req, err := s.client.NewRequest("POST", u, opt, options)
	if err != nil {
		return nil, nil, err
	}
	n := new(Note)
	resp, err := s.client.Do(req, n)
	if err != nil {
		return nil, resp, err
	}
	return n, resp, err
}
type UpdateIssueNoteOptions struct {
	Body *string `url:"body,omitempty" json:"body,omitempty"`
}
func (s *NotesService) UpdateIssueNote(pid interface{}, issue, note int, opt *UpdateIssueNoteOptions, options ...OptionFunc) (*Note, *Response, error) {
	project, err := parseID(pid)
	if err != nil {
		return nil, nil, err
	}
	u := fmt.Sprintf("projects/%s/issues/%d/notes/%d", url.QueryEscape(project), issue, note)
	req, err := s.client.NewRequest("PUT", u, opt, options)
	if err != nil {
		return nil, nil, err
	}
	n := new(Note)
	resp, err := s.client.Do(req, n)
	if err != nil {
		return nil, resp, err
	}
	return n, resp, err
}
func (s *NotesService) DeleteIssueNote(pid interface{}, issue, note int, options ...OptionFunc) (*Response, error) {
	project, err := parseID(pid)
	if err != nil {
		return nil, err
	}
	u := fmt.Sprintf("projects/%s/issues/%d/notes/%d", url.QueryEscape(project), issue, note)
	req, err := s.client.NewRequest("DELETE", u, nil, options)
	if err != nil {
		return nil, err
	}
	return s.client.Do(req, nil)
}