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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 GetGRRVersionString(self):
 """Returns the client installation-name and GRR version as a string."""

    client_info = self.startup_info.client_info
    client_name = client_info.client_description or client_info.client_name
    if client_info.client_version > 0:
      client_version = str(client_info.client_version)
    else:
      client_version = _UNKNOWN_GRR_VERSION
    return " ".join([client_name, client_version])