Note about missingArg not being found in baseR but rather 'methods'

[selkamand]

 required_args_are_missing : <anonymous>: no visible global function
    definition for ‘missingArg’
  Undefined global functions or variables:
    missingArg
  Consider adding
    importFrom("methods", "missingArg")
  to your NAMESPACE file (and ensure that your DESCRIPTION Imports field
  contains 'methods').

Easy fix is just to add explicit namespace methods::missingArg and import the methods package as a 'dependency'

Its not truly a dependency since methods is one of the base R packages (distributed with base R) so I don't mind this at all.

Otherwise we could just switch to an Rlang method for accomplishing the same thing. But if i had to bet - i suspect methods::missingArg is more likely to be stable over time than an equivalent Rlang solution so will go with this