An abstract filter.
        
            | Methods |  | 
        
        |  | 
            |  | __init__ | 
        
        | 
__init__ ( self )
 | 
            |  | _flush | 
        
        | 
_flush ( self )
 The _flush method should always flush the sink and should not
        be overridden. | 
            |  | attach | 
        
        | 
attach ( self,  filter )
 Attach a filter to this one. | 
            |  | close | 
        
        | 
close ( self )
 Close the filter.  Do an explicit flush first, then close the
        sink. | 
            |  | detach | 
        
        | 
detach ( self )
 Detach a filter from its sink. | 
            |  | flush | 
        
        | 
flush ( self )
 The flush method can be overridden. | 
            |  | last | 
        
        | 
last ( self )
 Find the last filter in this chain. | 
            |  | next | 
        
        | 
next ( self )
 Return the next filter/file-like object in the sequence, or None. | 
            |  | write | 
        
        | 
write ( self,  data )
 The standard write method; this must be overridden in subclasses. | 
            |  | writelines | 
        
        | 
writelines ( self,  lines )
 Standard writelines wrapper. |