Filter a set of entities based on method return. Use keyword arguments.
  
  Example:
    filtmeth(entities, id='123')
    filtmeth(entities, name='bart')

  Multiple filters are 'OR'.

def filtany(entities, **kw):
  """Filter a set of entities based on method return. Use keyword arguments.
  
  Example:
    filtmeth(entities, id='123')
    filtmeth(entities, name='bart')

  Multiple filters are 'OR'.
  """
  ret = set()
  for k,v in kw.items():
    for entity in entities:
      if getattr(entity, k)() == v:
        ret.add(entity)
  return ret