
I would like you to implement a module named TopModule with the following
interface. All input and output ports are one bit unless otherwise
specified.

 - input  in
 - input  state (2 bits)
 - output next_state (2 bits)
 - output out

The module should implement the following is the state transition table
for a Moore state machine with one input, one output, and four states.
Use the following state encoding: A=2'b00, B=2'b01, C=2'b10,
D=2'b11.Implement only the state transition logic and output logic (the
combinational logic portion) for this state machine. Given the current
state (state), compute the next_state and output (out) based on the state
transition table.

  State | Next state in=0, Next state in=1 | Output
  A     | A, B                             | 0
  B     | C, B                             | 0
  C     | A, D                             | 0
  D     | C, B                             | 1

