playing with relativity APIs

usage.py

m2m = M2M()
ch = M2MChain()
gr = M2MGraph()


# TRANSFORMING BETWEEN TYPES

chain(*ch.m2ms)  # kind of a copy
chain(ch)  # also results in copy

chain(ch.m2ms[1:])  # slices off left column

gr.chain(col1, col2, col3)  # returns a chain

gr.star(col1, col2, col3)  # returns M2MStar of 1-?2, 1->3

# "public" m2ms -- note this might be problematic b/c assignments
# to these data structures can screw up internal state
gr.m2ms[col1, col2]  # selecting M2M out of internal dict
ch.m2ms[1]  # selecting M2M out of internal list


# chain is a bit weird in that __getitem__ and __setitem__
# are not in sync with __iter__ -- [] accesses M2Ms, iter()
# goes "row-wise" down

# current iteration of chain
for row in chain:
  pass

# alternatives
for row in chain.tuples():
  pass

for row in chain.iter_tuples():
  pass