birdnotes.py: Objects to represent bird note files

This method adds the taxon-group content to the XML being built.

# - - -   B i r d F o r m . _ _ w r i t e T a x o n G r o u p

    def __writeTaxonGroup ( self, formNode ):
        """Attach taxon-group content to formNode.

          [ formNode is an et.Element ->
              formNode  +:=  self's taxon-group content ]
        """

The ab6 attribute is required. The rel attribute is optional, but if it is used, there must also be an alt attribute. Finally, the notable attribute is optional.

        #-- 1 --
        # [ formNode  +:=  an rnc.AB6_A attribute made from self.ab6 ]
        formNode.attrib [ rnc.AB6_A ]  =  self.ab6

        #-- 2 --
        # [ if self.rel ->
        #     formNode  :=  formNode with an rnc.REL_A attribute
        #         made from self.rel and an rnc.ALT_A attribute
        #         made from self.alt
        #   else -> I ]
        if  self.rel:
            formNode.attrib [ rnc.REL_A ]  =  self.rel
            formNode.attrib [ rnc.ALT_A ]  =  self.alt

        #-- 3 --
        if  self.notable:
            formNode.attrib [ rnc.NOTABLE_A ]  =  self.notable