Looks like it exists, and works (at least for strings):

  >>> 'test'.count('e')
  1
  >>> 'test'.count('')
  5
  >>> 'test'.count('tes')
  1
  >>> 'test'.count('t')
  2
  >>> 'test'.count('apple')
  0

Seems to be the equivalent of `in` on a string but with a count.