You're working on a project where you need to validate phone numbers using regular expressions in Python. Write Python code that accomplishes the following:

a$.$ Import the re module for regular expressions.

b$.$ Ask the user to enter a phone number.

c$.$ Use regular expressions to check if the entered phone number is valid according to the following requirements:

A valid phone number should consist of $10$ digits.

It may optionally include hyphens $("-")$ or spaces $("")$ as separators, but these separators should not appear consecutively.

The phone number should start with one of the following: $"0,""1,""2,""3,""4,""5,""6,""7,""8,"$ or $"9."$

d$.$ Print "Valid phone number" if the entered phone number is valid; otherwise, print "Invalid phone number."

Example Output:

Enter a phone number: $123-456-7890$

Valid phone number

Enter a phone number: $5555555555$

Valid phone number

Enter a phone number: $1234567890$

Invalid phone number

Enter a phone number: $0123456789$

Valid phone number

Python