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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 extract_issuer_ca_cert_url(cert_obj):
 """Extract issuer CA certificate URL from certificate. Certificates may include a URL where the root certificate for the CA which was used for signing the certificate can be downloaded. This function returns the URL if present. The primary use for this is to fix validation failure due to non-trusted issuer by downloading the root CA certificate from the URL and installing it in the local trust store. Args: cert_obj: cryptography.Certificate Returns: str: Issuer certificate URL if present, else None """

    for extension in cert_obj.extensions:
        if extension.oid.dotted_string == AUTHORITY_INFO_ACCESS_OID:
            authority_info_access = extension.value
            for access_description in authority_info_access:
                if access_description.access_method.dotted_string == CA_ISSUERS_OID:
                    return access_description.access_location.value