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  propertynames(x, private=false)

  Get a tuple or a vector of the properties (x.property) of an object x. This is typically the same as
  fieldnames(typeof(x)), but types that overload getproperty should generally overload propertynames as well to get
  the properties of an instance of the type.

  propertynames(x) may return only "public" property names that are part of the documented interface of x. If you want
  it to also return "private" fieldnames intended for internal use, pass true for the optional second argument. REPL
  tab completion on x. shows only the private=false properties.

  See also: hasproperty, hasfield.