isInverseMap -- checks whether a rational map is the inverse of another

• Usage:

  isInverseMap(phi,psi)

• Inputs:
  • phi, a ring map, representing a rational map $\Phi:X \dashrightarrow Y$
  • psi, a ring map, representing a rational map $\Psi:Y \dashrightarrow X$
• Outputs:
  • a Boolean value, according to the condition that the composition $\Psi\,\Phi:X \dashrightarrow X$ coincides with the identity of $X$ (as a rational map)