RO functional syntax will not parse

[cmungall]

[I will commit a test right after this]

ERROR: test_ro (tests.test_ontologies.test_ro.RelationOntologyTestCase)
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Traceback (most recent call last):
  File "/Users/cjm/repos/funowl/tests/test_ontologies/test_ro.py", line 13, in test_ro
    doc = to_python(os.path.join(datadir, 'ro.ofn'))
  File "/Users/cjm/repos/funowl/funowl/converters/functional_converter.py", line 353, in to_python
    fparse(to_bytes_array(defn), 0, consumer)
  File "/Users/cjm/repos/funowl/funowl/converters/functional_converter.py", line 301, in fparse
    start = fparse(inp, start, lambda f: o.add_arg(f))
  File "/Users/cjm/repos/funowl/funowl/converters/functional_converter.py", line 310, in fparse
    consumer(OWLFunc(m.group(1).decode(), parse_args(body.decode())).decl)
  File "/Users/cjm/repos/funowl/funowl/converters/functional_converter.py", line 219, in parse_args
    rval.append(OWLFunc(m.group(1), parse_args(args.decode())))
  File "/Users/cjm/repos/funowl/funowl/converters/functional_converter.py", line 219, in parse_args
    rval.append(OWLFunc(m.group(1), parse_args(args.decode())))
  File "/Users/cjm/repos/funowl/funowl/converters/functional_converter.py", line 219, in parse_args
    rval.append(OWLFunc(m.group(1), parse_args(args.decode())))
  File "/Users/cjm/repos/funowl/funowl/converters/functional_converter.py", line 68, in __init__
    self.decl = self.eval(function, body)
  File "/Users/cjm/repos/funowl/funowl/converters/functional_converter.py", line 113, in eval
    raise NotImplemented(f"Method {function} is not implemented")
TypeError: 'NotImplementedType' object is not callable