Namespaces are the environment where all the functions of a package
live. The parent environments of namespaces are the imports
environments, which contain all the functions imported from other
packages.
ns_env(x = caller_env())ns_imports_env(x = caller_env())
ns_env_name(x = caller_env())
For ns_env(), the name of a package or an environment as a
string.
An environment (the current environment by default).
A function.
In the latter two cases, the environment ancestry is searched for
a namespace with base::topenv(). If the environment doesn't
inherit from a namespace, this is an error.
pkg_env()