func GetConversion(in cty.Type, out cty.Type) Conversion {
	return retConversion(getConversion(in, out, false))
}
GetConversion returns a Conversion between the given in and out Types if
a safe one is available, or returns nil otherwise.
package convert
import (
	"errors"
	"github.com/zclconf/go-cty/cty"
)
type Conversion func(in cty.Value) (out cty.Value, err error)