New SD Mechanism development : UnmarshalYAML method getting called twice

[Mayur R]

I am developing new SD mechanism in Prometheus for Oracle Cloud Infrastructure.

and during debugging I am observing that it 

 the "unmarshall" method 

func (c *SDConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {...}

is getting called twice.

Is it expected?

As far as I understood the Prometheus framework, it should get called only once at the start.

I am new to golang, doubting if there is some problem with my setup.