Create a concrete version of the replaced string
    (replace ONLY th efirst occurrence of the pattern)

    :param initial_string: string in which the pattern needs to be replaced
    :param pattern_to_be_replaced: substring that has to be replaced inside initial_string
    :param replacement_poattern: pattern that has to be inserted in initial_string t replace
                                 pattern_to_be_replaced
    :return: a concrete representation of the replaced string

def StrReplace(initial_string, pattern_to_be_replaced, replacement_pattern):
    """
    Create a concrete version of the replaced string
    (replace ONLY th efirst occurrence of the pattern)

    :param initial_string: string in which the pattern needs to be replaced
    :param pattern_to_be_replaced: substring that has to be replaced inside initial_string
    :param replacement_poattern: pattern that has to be inserted in initial_string t replace
                                 pattern_to_be_replaced
    :return: a concrete representation of the replaced string
    """
    new_value = initial_string.value.replace(pattern_to_be_replaced.value,
                                             replacement_pattern.value,
                                             1)
    return StringV(new_value)