def command(commands)
      command = Command.new(commands)
      server.remote_expr("VimrunnerEvaluateCommandOutput('#{command}')").tap do |output|
        raise InvalidCommandError.new(output) if output =~ /^Vim(\(call\))?:E\d+:/
      end
    end
def command(commands)
      command = Command.new(commands)
      server.remote_expr("VimrunnerEvaluateCommandOutput('#{command}')").tap do |output|
        raise InvalidCommandError.new(output) if output =~ /^Vim(\(call\))?:E\d+:/
      end
    end
Public: Executes the given command in the Vim instance and returns its
 output, stripping all surrounding whitespace.

 Returns the String output.
 Raises InvalidCommandError if the command is not recognised by vim.