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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def valid_hash_value(hashname):
 """Return true if given value is a valid, recommended hash name according to the STIX 2 specification. """

    custom_hash_prefix_re = re.compile(r"^x_")
    if hashname in enums.HASH_ALGO_OV or custom_hash_prefix_re.match(hashname):
        return True
    else:
        return False