I am trying to run this command to clump in the TwoSample MR package but I am encountering the following error:

options(ieugwasr_api = 'gwas-api.mrcieu.ac.uk/')

#Clumping the exposure data 
exposure_data <- clump_data(exposure_data, clump_r2 = 0.001)

exposure_data <- clump_data(exposure_data, clump_r2 = 0.001)
Please look at vignettes for options on running this locally if you need to run many instances of this command.
Clumping mraR9f, 200 variants, using EUR population reference
No encoding supplied: defaulting to UTF-8.
Error in mtfrm.default(list(url = "https://api.opengwas.io/api/ld/clump",  : 
  cannot mtfrm