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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 __dbfHeaderLength(self):

 """Retrieves the header length of a dbf file header."""

        if not self.__dbfHdrLength:
            if not self.dbf:
                raise ShapefileException("Shapefile Reader requires a shapefile or file-like object. (no dbf file found)")
            dbf = self.dbf
            (self.numRecords, self.__dbfHdrLength) = \
                    unpack("<xxxxLH22x", dbf.read(32))
        return self.__dbfHdrLength