test dynamic output declaration in python ecto cells.

dynamic_out.py

import ecto

class FanCell(ecto.Cell):
    def declare_params(self, p):
        p.declare("N", "number of outputs", 3)
    def declare_io(self, p, i, o):
        for i in range(p.N):
            o.declare("out%d"%i, "output %d"%i, None)


class FanCellStatic(ecto.Cell):
    @staticmethod
    def declare_params(p):
        p.declare("N", "number of outputs", 3)
    @staticmethod
    def declare_io(p, i, o):
        for i in range(p.N):
            o.declare("out%d"%i, "output %d"%i, None)

c1 = FanCell(N=2)
print c1.outputs
c2 = FanCellStatic(N=7)
print c2.outputs

assert len(c1.outputs) == 2
assert len(c2.outputs) == 7