How to use the pipupgrade.util.environ.getenv function in pipupgrade

parser.add_argument("--github-reponame",
        help    = "Target GitHub Repository Name",
        default = getenv("GITHUB_REPONAME")
    )
    parser.add_argument("--github-username",
        help    = "Target GitHub Username",
        default = getenv("GITHUB_USERNAME")
    )
    parser.add_argument("--target-branch",
        help    = "Target Branch",
        default = getenv("TARGET_BRANCH", "master")
    )
    parser.add_argument("-j", "--jobs",
        type    = int,
        help    = "Number of Jobs to be used.",
        default = getenv("JOBS", mp.cpu_count())
    )
    parser.add_argument("-u", "--user",
        action  = "store_true",
        default = getenv("USER_ONLY", False),
        help    = "Install to the Python user install directory for environment \
                    variables and user configuration."
    )
    parser.add_argument("--no-included-requirements",
        action  = "store_true",
        default = getenv("NO_INCLUDED_REQUIREMENTS", False),
        help    = "Avoid updating included requirements."
    )
    parser.add_argument("--no-cache",
        action  = "store_true",
        default = getenv("NO_CACHE", False),
        help    = "Avoid fetching latest updates from PyPI server."

)
    parser.add_argument("--upgrade-type",
        choices = ("major", "minor", "patch"),
        nargs   = "+",
        default = ["minor", "patch"],
        help    = "Upgrade Type"
    )
    parser.add_argument("-l", "--latest",
        action  = "store_true",
        default = getenv("UPDATE_LATEST", False),
        help    = "Update all packages to latest."
    )
    parser.add_argument("-f", "--format",
        choices = ["table", "tree", "json", "yaml"],
        help    = "Display packages format.",
        default = getenv("DISPLAY_FORMAT", "table")
    )
    parser.add_argument("-a", "--all",
        action  = "store_true",
        default = getenv("DISPLAY_ALL_PACKAGES", False),
        help    = "List all packages."
    )
    parser.add_argument("--pip",
        action  = "store_true",
        default = getenv("UPDATE_PIP", False),
        help    = "Update pip."
    )
    parser.add_argument("-s", "--self",
        action  = "store_true",
        help    = "Update %s." % __name__
    )
    parser.add_argument("-r", "--requirements",

default = getenv("UPDATE_LATEST", False),
        help    = "Update all packages to latest."
    )
    parser.add_argument("-f", "--format",
        choices = ["table", "tree", "json", "yaml"],
        help    = "Display packages format.",
        default = getenv("DISPLAY_FORMAT", "table")
    )
    parser.add_argument("-a", "--all",
        action  = "store_true",
        default = getenv("DISPLAY_ALL_PACKAGES", False),
        help    = "List all packages."
    )
    parser.add_argument("--pip",
        action  = "store_true",
        default = getenv("UPDATE_PIP", False),
        help    = "Update pip."
    )
    parser.add_argument("-s", "--self",
        action  = "store_true",
        help    = "Update %s." % __name__
    )
    parser.add_argument("-r", "--requirements",
        action  = "append",
        help    = "Path(s) to requirements.txt file."
    )
    parser.add_argument("--pipfile",
        action  = "append",
        help    = "Path(s) to Pipfile"
    )
    parser.add_argument("-i", "--interactive",
        action  = "store_true",

parser.add_argument("-i", "--interactive",
        action  = "store_true",
        default = getenv("INTERACTIVE", False),
        help    = "Interactive Mode."
    )
    parser.add_argument("-p", "--project",
        action  = "append",
        help    = "Path(s) to Project"
    )
    parser.add_argument("--git-username",
        help    = "Git Username",
        default = getenv("GIT_USERNAME")
    )
    parser.add_argument("--git-email",
        help    = "Git Email",
        default = getenv("GIT_EMAIL")
    )
    parser.add_argument("--pull-request",
        action  = "store_true",
        help    = "Perform a Pull Request."
    )
    parser.add_argument("--github-access-token",
        help    = "GitHub Access Token",
        default = getenv("GITHUB_ACCESS_TOKEN")
    )
    parser.add_argument("--github-reponame",
        help    = "Target GitHub Repository Name",
        default = getenv("GITHUB_REPONAME")
    )
    parser.add_argument("--github-username",
        help    = "Target GitHub Username",
        default = getenv("GITHUB_USERNAME")

default = getenv("TARGET_BRANCH", "master")
    )
    parser.add_argument("-j", "--jobs",
        type    = int,
        help    = "Number of Jobs to be used.",
        default = getenv("JOBS", 1)
    )
    parser.add_argument("-u", "--user",
        action  = "store_true",
        default = getenv("USER_ONLY", False),
        help    = "Install to the Python user install directory for environment \
                    variables and user configuration."
    )
    parser.add_argument("--no-included-requirements",
        action  = "store_true",
        default = getenv("NO_INCLUDED_REQUIREMENTS", False),
        help    = "Avoid updating included requirements."
    )
    parser.add_argument("--no-cache",
        action  = "store_true",
        default = getenv("NO_CACHE", False),
        help    = "Avoid fetching latest updates from PyPI server."
    )
    parser.add_argument("-o", "--output",
        default = getenv("OUTPUT_FILE"),
        help    = "Print Output to File."
    )
    parser.add_argument("--force",
        action  = "store_true",
        default = getenv("FORCE", False),
        help    = "Force search for files within a project."
    )

)
    parser.add_argument("packages",
        nargs   = "*",
        help    = "Packages to Upgrade."
    )
    parser.add_argument("--ignore",
        action  = "append",
        help    = "Ignore packages to upgrade."
    )
    parser.add_argument("--pip-path",
        action  = "append",
        help    = "Path to pip executable to be used."
    )
    parser.add_argument("-y", "--yes",
        action  = "store_true",
        default = getenv("ACCEPT_ALL_DIALOGS", False),
        help    = "Confirm for all dialogs."
    )
    parser.add_argument("-c", "--check",
        action  = "store_true",
        default = getenv("DRY_RUN", False),
        help    = "Perform a dry-run, avoid updating packages."
    )
    parser.add_argument("--upgrade-type",
        choices = ("major", "minor", "patch"),
        nargs   = "+",
        default = ["minor", "patch"],
        help    = "Upgrade Type"
    )
    parser.add_argument("-l", "--latest",
        action  = "store_true",
        default = getenv("UPDATE_LATEST", False),

parser.add_argument("--ignore",
        action  = "append",
        help    = "Ignore packages to upgrade."
    )
    parser.add_argument("--pip-path",
        action  = "append",
        help    = "Path to pip executable to be used."
    )
    parser.add_argument("-y", "--yes",
        action  = "store_true",
        default = getenv("ACCEPT_ALL_DIALOGS", False),
        help    = "Confirm for all dialogs."
    )
    parser.add_argument("-c", "--check",
        action  = "store_true",
        default = getenv("DRY_RUN", False),
        help    = "Perform a dry-run, avoid updating packages."
    )
    parser.add_argument("--upgrade-type",
        choices = ("major", "minor", "patch"),
        nargs   = "+",
        default = ["minor", "patch"],
        help    = "Upgrade Type"
    )
    parser.add_argument("-l", "--latest",
        action  = "store_true",
        default = getenv("UPDATE_LATEST", False),
        help    = "Update all packages to latest."
    )
    parser.add_argument("-f", "--format",
        choices = ["table", "tree", "json", "yaml"],
        help    = "Display packages format.",

action  = "append",
        help    = "Path to pip executable to be used."
    )
    parser.add_argument("-y", "--yes",
        action  = "store_true",
        default = getenv("ACCEPT_ALL_DIALOGS", False),
        help    = "Confirm for all dialogs."
    )
    parser.add_argument("-c", "--check",
        action  = "store_true",
        default = getenv("DRY_RUN", False),
        help    = "Perform a dry-run, avoid updating packages."
    )
    parser.add_argument("-l", "--latest",
        action  = "store_true",
        default = getenv("UPDATE_LATEST", False),
        help    = "Update all packages to latest."
    )
    parser.add_argument("-f", "--format",
        choices = ["table", "tree", "json", "yaml"],
        help    = "Display packages format.",
        default = getenv("DISPLAY_FORMAT", "table")
    )
    parser.add_argument("-a", "--all",
        action  = "store_true",
        default = getenv("DISPLAY_ALL_PACKAGES", False),
        help    = "List all packages."
    )
    parser.add_argument("--pip",
        action  = "store_true",
        default = getenv("UPDATE_PIP", False),
        help    = "Update pip."

)
    parser.add_argument("--pull-request",
        action  = "store_true",
        help    = "Perform a Pull Request."
    )
    parser.add_argument("--github-access-token",
        help    = "GitHub Access Token",
        default = getenv("GITHUB_ACCESS_TOKEN")
    )
    parser.add_argument("--github-reponame",
        help    = "Target GitHub Repository Name",
        default = getenv("GITHUB_REPONAME")
    )
    parser.add_argument("--github-username",
        help    = "Target GitHub Username",
        default = getenv("GITHUB_USERNAME")
    )
    parser.add_argument("--target-branch",
        help    = "Target Branch",
        default = getenv("TARGET_BRANCH", "master")
    )
    parser.add_argument("-j", "--jobs",
        type    = int,
        help    = "Number of Jobs to be used.",
        default = getenv("JOBS", mp.cpu_count())
    )
    parser.add_argument("-u", "--user",
        action  = "store_true",
        default = getenv("USER_ONLY", False),
        help    = "Install to the Python user install directory for environment \
                    variables and user configuration."
    )

parser.add_argument("--github-reponame",
        help    = "Target GitHub Repository Name",
        default = getenv("GITHUB_REPONAME")
    )
    parser.add_argument("--github-username",
        help    = "Target GitHub Username",
        default = getenv("GITHUB_USERNAME")
    )
    parser.add_argument("--target-branch",
        help    = "Target Branch",
        default = getenv("TARGET_BRANCH", "master")
    )
    parser.add_argument("-j", "--jobs",
        type    = int,
        help    = "Number of Jobs to be used.",
        default = getenv("JOBS", 1)
    )
    parser.add_argument("-u", "--user",
        action  = "store_true",
        default = getenv("USER_ONLY", False),
        help    = "Install to the Python user install directory for environment \
                    variables and user configuration."
    )
    parser.add_argument("--no-included-requirements",
        action  = "store_true",
        default = getenv("NO_INCLUDED_REQUIREMENTS", False),
        help    = "Avoid updating included requirements."
    )
    parser.add_argument("--no-cache",
        action  = "store_true",
        default = getenv("NO_CACHE", False),
        help    = "Avoid fetching latest updates from PyPI server."