Creating new class using boostrap less mixins?

I have one element

HTML

<div class="content col-md-10 col-md-offset-1">
</div>

What i need in LESS i something like this

.content{
  .col-md-10;
  .col-md-offset-1;
}

That later i can use shortner code like this

<div class="content col-md-10 col-md-offset-1">
</div>

I know i must use only content like this

<div class="content">
</div>

I have tried something like this but does not work?

.content{
	.make-md-column(10);
	.make-md-offset(1);
}

Update

It's called <code>make-md-<b>column</b>-offset</code> not make-md-offset

Running the following through any Online Less Compiler should work:

<!-- language: lang-css -->

@grid-gutter-width: 30px;
@screen-md-min: 992px;
@grid-columns: 12;

// Generate the medium columns
.make-md-column(@columns; @gutter: @grid-gutter-width) {
  position: relative;
  // Prevent columns from collapsing when empty
  min-height: 1px;
  // Inner gutter via padding
  padding-left:  (@gutter / 2);
  padding-right: (@gutter / 2);

  // Calculate width based on number of columns available
  @media (min-width: @screen-md-min) {
    float: left;
    width: percentage((@columns / @grid-columns));
  }
}

// Generate the medium column offsets
.make-md-column-offset(@columns) {
  @media (min-width: @screen-md-min) {
    margin-left: percentage((@columns / @grid-columns));
  }
}

.content{
    .make-md-column(10);
    .make-md-column-offset(1);
}

Original

My guess would be you have something missing from the build process like importing the mixin functions or variables.

Here is the section on bootstrap grid mixins:
http://getbootstrap.com/css/#grid-less

Here is a Example Usage:

<!-- language: lang-css -->

.content-secondary {
  .make-lg-column(3);
  .make-lg-column-offset(1);
}

So your syntax looks fine. I'd make sure you don't have any build errors.