Bird taxonomy system: internal maintenance specification

Retrieves the Taxon for a given bird code, if any.

# - - -   T x n y . l o o k u p A b b r   - - -

    def lookupAbbr ( self, abbr ):
        """Look up a taxon by bird code.
        """
        return self.__abbrMap [ abbr.upper().ljust(ABBR_L) ]