Debugf writes a debug message to stderr.

Error writes an error message to stderr.

Printf writes a regular log message to stderr.

Printv writes a variable as a regular log message to stderr TODO: would be nice if this could print the variable name (and ideally the private fields too, if reflection allows us access to them).

DebugEnabled controls whether Debug log messages are generated.

ErrorEnabled controls whether Error log messages are generated.

InfoEnabled controls whether "regular" log messages are generated.