code: def _compile_update_from(self, query):
          
          if not query.joins:
              return ""
  
          froms = []
  
          for join in query.joins:
              froms.append(self.wrap_table(join.table))
  
          if len(froms):
              return " FROM %s" % ", ".join(froms)
  
          return ""
docs: Compile the "from" clause for an update with a join.
  
          :param query: A QueryBuilder instance
          :type query: QueryBuilder
  
          :return: The compiled sql
          :rtype: str