human
Solve the following python programming problem given the following code:
def cast_relationship(obj, entities = None) : 
    def get_type(r) : 
        if isinstance (r, string) : 
            return r 
else : 
            if hasattr (r, 'type') : 
                return r.type () 
else : 
                if (isinstance (r, tuple) and (len (r) == 2) and isinstance (r [0], string)) : 
                    return r [0] 
else : 
                    raise ValueError (('Cannot determine relationship type from %r' % r)) 
def get_properties(r) : 
        if isinstance (r, string) : 
            return { 
                
} 
else : 
            if (hasattr (r, 'type') and callable (r.type)) : 
                return dict (r) 
else : 
                if hasattr (r, 'properties') : 
                    return r.properties 
else : 
                    if (isinstance (r, tuple) and (len (r) == 2) and isinstance (r [0], string)) : 
                        return dict (r [1]) 
else : 
                        raise ValueError (('Cannot determine properties from %r' % r)) 
if isinstance (obj, Relationship) : 
        return obj 
else : 
        if isinstance (obj, tuple) : 
            if (len (obj) == 3) : 
                (start_node, t, end_node) = obj 
                properties = get_properties (t) 
else : 
                if (len (obj) == 4) : 
                    (start_node, t, end_node, properties) = obj 
                    properties = dict (get_properties (t), ** properties) 
else : 
                    raise TypeError (('Cannot cast relationship from %r' % obj)) 
else : 
            raise TypeError (('Cannot cast relationship from %r' % obj)) 
if entities : 
        if isinstance (start_node, integer) : 
            start_node = entities [start_node] 
if isinstance (end_node, integer) : 
            end_node = start_node [end_node] 
return Relationship (start_node, get_type (t), end_node, ** properties) 

    
    

    Fix the buggy line: end_node = start_node [end_node]
assistant
#Here is Python code to determine relationship type from %r' % r)) 
.

end_node = entities [end_node]