code: def box_add(self, name, url, provider=None, force=False):
          '''
          Adds a box with given name, from given url.
  
          force: If True, overwrite an existing box if it exists.
          '''
          force_opt = '--force' if force else None
          cmd = ['box', 'add', name, url, force_opt]
          if provider is not None:
              cmd += ['--provider', provider]
  
          self._call_vagrant_command(cmdf box_add(self, name, url, provider=None, force=False):
          '''
          Adds a box with given name, from given url.
  
          force: If True, overwrite an existing box if it exists.
          '''
          force_opt = '--force' if force else None
          cmd = ['box', 'add', name, url, force_opt]
          if provider is not None:
              cmd += ['--provider', provider]
  
          self._call_vagrant_command(cmd)
docs: Adds a box with given name, from given url.
  
          force: If True, overwrite an existing box if it exists.