Wrap customdata, so far you can access the data layers in a pythonic way but not manipulate the customdata yet.
provides dictionary like access to customdata layers, eg:
texpoly = bm.faces.tex["UVMap"]
print(bm.verts.shape.keys()) # un-intended pun, keys() works on all layers.
print("MyInt" in bm.edges.int) # __contains__
layer = bm.faces.get("CheckForLayer")