def StrReplace(initial_string, pattern_to_be_replaced, replacement_pattern):
new_value = initial_string.value.replace(pattern_to_be_replaced.value,<EOL>replacement_pattern.value,<EOL><NUM_LIT:1>)<EOL>return StringV(new_value)<EOL>
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