Adds a linguistic processor to the header
        @type my_lp: L{Clp}
        @param my_lp: linguistic processor object
        @type layer: string
        @param layer: the layer to which the processor is related to

def add_linguistic_processor(self, layer, my_lp):
        """
        Adds a linguistic processor to the header
        @type my_lp: L{Clp}
        @param my_lp: linguistic processor object
        @type layer: string
        @param layer: the layer to which the processor is related to
        """
        if self.header is None:
            self.header = CHeader(type=self.type)
            self.root.insert(0,self.header.get_node())
        self.header.add_linguistic_processor(layer,my_lp)