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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 update_property_node(node_to_insert, field_uri):
 """ Helper function - generates a SetItemField which tells Exchange you want to overwrite the contents of a field."""

  root = T.SetItemField(
            T.FieldURI(FieldURI=field_uri),
            T.CalendarItem(node_to_insert)
        )
  return root