human
expandvars non defined.
assistant
Here is a Python function to expandvars non defined

import re

def expandvars(text):
    """Expand all variables in a string.

    :param str text:
    :rtype: str
    :return:
    """
    return text.replace('$', '$1')

# Enter the string
string = "${username}${password}"

# Calling the function
print((expandvars(string)))

#Example Output
# $1{username}$1{password}

#Remember to inspect code for bugs.