code: def _is_mostly_subdomain_compatible(bucket_name):
      
      return (bucket_name.lower() == bucket_name and
              len(bucket_name) >= 3 and
              len(bucket_name) <= 63 and
              '_' not in bucket_name and
              '..' not in bucket_name and
              '-.' not in bucket_name and
              '.-' not in bucket_name and
              not bucket_name.startswith('-') and
              not bucket_name.endswith('-') and
              not bucket_name.startswith('.') and
              not bucket_name.endswith('.') and
              not _is_ipv4_like(bucket_name))
docs: Returns True if SubdomainCallingFormat can be used...mostly
  
      This checks to make sure that putting aside certificate validation
      issues that a bucket_name is able to use the
      SubdomainCallingFormat.