func (env *Env) Exists(key string) bool {
	_, exists := env.Map()[key]
	return exists
}
Exists checks whether the given key is defined in the internal Env
representation.
package docker
import (
	"encoding/json"
	"fmt"
	"io"
	"strconv"
	"strings"
)
type Env []string
func (env *Env) Get(key string) (value string) {
	return env.Map()[key]
}