Class ThresholdScreener

source code

        object --+    
                 |    
SimilarityScreener --+
                     |
                    ThresholdScreener

Used to return all compounds that have a similarity
 to the probe beyond a threshold value

**Notes**:

  - This is as lazy as possible, so the data source isn't
    queried until the client asks for a hit.

  - In addition to being lazy, this class is as thin as possible.
    (Who'd have thought it was possible!)
    Hits are *not* stored locally, so if a client resets
    the iteration and starts over, the same amount of work must
    be done to retrieve the hits.
    
  - The thinness and laziness forces us to support only forward
    iteration (not random access)

x.__init__(...) initializes x; see help(type(x)) for signature

used to reset our internal state so that iteration
starts again from the beginning

returns an iterator for this screener