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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def to_placeholder(self, name=None, db_type=None):
 """Returns a placeholder for the specified name, by applying the instance's format strings. :name: if None an unamed placeholder is returned, otherwise a named placeholder is returned. :db_type: if not None the placeholder is typecast. """

    if name is None:
      placeholder = self.unnamed_placeholder
    else:
      placeholder = self.named_placeholder.format(name)

    if db_type:
      return self.typecast(placeholder, db_type)
    else:
      return placeholder