import re


def extract_number(line):
    """
    Extracts the phone number from a vCard-file line,
    by removing everything but numbers and '+'

    Arguments:
        line {string} -- the line to extract the phone number from

    Returns:
        string -- the phone number
    """

    line = line[line.index(":")+1:].rstrip()
    line = re.sub('[^0-9+]', '', line)
    return line