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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 _vcf_is_strelka(variant_file, variant_metadata):
 """Return True if variant_file given is in strelka format """

    if "strelka" in variant_file.lower():
        return True
    elif "NORMAL" in variant_metadata["sample_info"].keys():
        return True
    else:
        vcf_reader = vcf.Reader(open(variant_file, "r"))
        try:
            vcf_type = vcf_reader.metadata["content"]
        except KeyError:
            vcf_type = ""
        if "strelka" in vcf_type.lower():
            return True
    return False