title: Simple count of number of records in ManyToMany table
body: <pre><code>class Author(models.Model):
     name = models.CharField(max_length=100)
     age = models.IntegerField()
     friends = models.ManyToManyField('self', blank=True)
  
  class Publisher(models.Model):
     name = models.CharField(max_length=300)
     num_awards = models.IntegerField()
  
  class Book(models.Model):
     isbn = models.CharField(max_length=9)
     name = models.CharField(max_length=300)
     pages = models.IntegerField()
     price = models.DecimalField(max_digits=10, decimal_places=2)
     rating = models.FloatField()
     authors = models.ManyToManyField(Author)
     publisher = models.ForeignKey(Publisher)
     pubdate = models.DateField()
  
  class Store(models.Model):
     name = models.CharField(max_length=300)
     books = models.ManyToManyField(Book)
  </code></pre>
  
  <p>I think I'm missing something really obvious but how do I get a count for the number of records created in this many-to-many table <code>authors = models.ManyToManyField(Author)</code>?</p>