Parses the protein tag to get the names and EC numbers.

def _parse_organism_tag(self):
        '''Parses the protein tag to get the names and EC numbers.'''
        organism_name_types = UniProtACEntry.organism_name_types
        self.organisms = []
        organism_tags = [child for child in self.entry_tag.childNodes if child.nodeType == child.ELEMENT_NODE and child.tagName == 'organism']
        assert(len(organism_tags) == 1)
        for organism_tag in organism_tags:
            names = dict.fromkeys(organism_name_types, None)
            for name_tag in [child for child in organism_tag.childNodes if child.nodeType == child.ELEMENT_NODE and child.tagName == 'name']:
                name_type = name_tag.getAttribute("type")
                assert(name_type in organism_name_types)
                names[name_type] = name_tag.firstChild.nodeValue.strip()
            assert(names.get('scientific'))
            self.organisms.append(names)