pub fn env_var_from_key(&self, key: &str) -> Option<String> {
        let matches = self.key.matches(key)?;
        let env_var_name = self.env_var.stringify(&matches);
        Some(env_var_name)
    }
/// If the provided key matches this mapping, return the
/// environment variable name it corresponds to, else None.
If the provided key matches this mapping, return the
environment variable name it corresponds to, else None.
If the provided key matches this mapping return the environment variable name it corresponds to else None .
pub fn env_var_from_key(&self, key: &str) -> Option<String> {
        let matches = self.key.matches(key)?;
        let env_var_name = self.env_var.stringify(&matches);
        Some(env_var_name)
    }
pub fn env_var_from_key ( & self , key : & str ) -> Option < String > { let matches = self . key . matches ( key ) ? ; let env_var_name = self . env_var . stringify ( & matches ) ; Some ( env_var_name ) }
If the provided key matches this mapping, return the
environment variable name it corresponds to, else None.
If the provided key matches this mapping return the environment variable name it corresponds to else None .
&self
key
&str
&self
key
&str