runtime error - Buffers not working in vim -

my buffers not working reason. when click <leader>b says

not editor command: buffers

this .vimrc file:

set nocompatible              " required filetype off                  " required  set rtp+=~/.vim/bundle/vundle.vim call vundle#begin()  " required plugin 'vundlevim/vundle.vim'  " general plugin 'scrooloose/nerdtree' plugin 'kien/ctrlp.vim' plugin 'scrooloose/syntastic' plugin 'tpope/vim-commentary'  " user interface plugin 'altercation/vim-colors-solarized' plugin 'jarrodctaylor/vim-256-color-schemes' plugin 'jarrodctaylor/vim-reflection' plugin 'vim-airline/vim-airline-themes' plugin 'bling/vim-airline'  " programming plugin 'mattn/emmet-vim' plugin 'tpope/vim-surround' plugin 'leafgarland/typescript-vim'  " languages plugin 'pangloss/vim-javascript' plugin 'davidhalter/jedi-vim'   " plugins must above line!!  call vundle#end()            " required filetype  plugin indent on   " required  " non-plugin stuff after line!!  " map leader , let mapleader=','  set t_co=256 syntax on  set nobackup                           " don't write backup files set noswapfile                         " ain't nobody got time swap files set noerrorbells                       " don't beep set nowrap                             " not wrap lines set shiftwidth=4                       " number of spaces use each step of indent set showcmd                            " display incomplete commands in bottom line of screen set tabstop=4                          " number of spaces <tab> counts set undolevels=1000                    " never can careful when comes undoing set hidden                             " don't unload buffer when switch between them. saves undo history set visualbell                         " visual bell instead of beeping set wildmenu                           " command-line completion in enhanced mode set shell=bash                         " required let zsh know how run things on command line set ttimeoutlen=50                     " fix delay when escaping insert esc set noshowmode                         " hide default mode text (e.g. -- insert -- below statusline) set showbreak=↪\ set synmaxcol=256 set scrolloff=3 set clipboard=unnamed au bufnewfile,bufread *.json set ft=javascript  " status line / visual configuration  syntax enable set t_co=256 set t_ut= hi clear hi string ctermfg=81 ctermbg=none cterm=none guifg=#5fd7ff guibg=none gui=none hi cursorline cterm=none ctermbg=darkred ctermfg=white  set laststatus=2                                    " make second last line of vim our status line let g:airline_theme='understated'                   " use custom theme wrote let g:airline_left_sep=''                           " no separator seem funky let g:airline_right_sep=''                          " no separator seem funky let g:airline#extensions#branch#enabled = 0         " not show git branch in status line let g:airline#extensions#syntastic#enabled = 1      " show syntastic warnings in status line let g:airline#extensions#tabline#show_buffers = 0   " not list buffers in status line let g:airline_section_x = ''                        " not list filetype or virtualenv in status line let g:airline_section_y = '[r%04l,c%04v] [len=%l]'  " replace file encoding , file format info file position let g:airline_section_z = ''                        " not show default file position info let g:airline#extensions#virtualenv#enabled = 0 autocmd bufreadpost quickfix nnoremap <buffer> <cr> :.cc<cr> autocmd bufreadpost quickfix nnoremap <buffer> o :.cc<cr> nnoremap <leader>w :%s/\s\+$//<cr>:let @/=''<cr> let g:syntastic_check_on_open=1                   " check errors when file loaded let g:syntastic_loc_list_height=5                 " height of error list defaults 10 let g:syntastic_python_checkers = ['flake8']      " sets flake8 default checking python files let g:syntastic_javascript_checkers = ['jshint']  " sets jshint our javascript linter let g:syntastic_filetype_map = { 'handlebars.html': 'handlebars' } let g:syntastic_mode_map={ 'mode': 'active',                      \ 'active_filetypes': [],                      \ 'passive_filetypes': ['html', 'handlebars'] }  set tags=./.ctags,.ctags; let g:nerdtreemapjumpnextsibling = '' let g:nerdtreemapjumpprevsibling = '' let g:gundo_preview_bottom = 1 let g:markdown_fold_style = 'nested' let g:markdown_fenced_languages = ['python', 'sh', 'vim', 'javascript', 'html', 'css', 'c', 'sql'] let g:indent_guides_start_level = 2 let g:indent_guides_guide_size = 1 let g:indent_guides_exclude_filetypes = ['help', 'nerdtree'] let g:indent_guides_auto_colors = 0 autocmd vimenter,colorscheme * :hi indentguidesodd  ctermbg=238 autocmd vimenter,colorscheme * :hi indentguideseven ctermbg=249  function! s:deletebuffer()     let line = getline('.')     let bufid = line =~ '\[\d\+\*no name\]$' ? str2nr(matchstr(line, '\d\+'))         \ : fnamemodify(line[2:], ':p')     exec "bd" bufid     exec "norm \<f5>" endfunction " nerdtree configuration let g:nerdtreechdirmode=2 let g:nerdtreeignore=['\.rbc$', '\~$', '\.pyc$', '\.db$', '\.sqlite$', '__pycache__'] let g:nerdtreesortorder=['^__\.py$', '\/$', '*', '\.swp$', '\.bak$', '\~$'] let g:nerdtreeshowbookmarks=1 let g:nerdtree_tabs_focus_on_files=1 let g:nerdtreemapopenintabsilent = '<rightmouse>' let g:nerdtreewinsize = 50 set wildignore+=*/tmp/*,*.so,*.swp,*.zip,*.pyc,*.db,*.sqlite nnoremap <silent> <f2> :nerdtreefind<cr> nmap <f3> :nerdtreetoggle<cr>  " buffer configuration nnoremap <silent> <leader>b :buffers<cr> " close buffer  nnoremap <leader>c :bd<cr> 

can tell me if missed something? accept tips on upgrading vimrc file feel free give tips :) want fix problem. please tell me should remove or add working again. working before. appeared suddenly.

maybe typo, see :h buffers
please change following line (lowercase b in :buffers)

nnoremap <silent> <leader>b :buffers<cr> 

to

nnoremap <silent> <leader>b :buffers<cr>