code: def Fmask(Fimg, dfnum, dfdenom, pvalue=1.0e-04):
      """
      Create mask for use in estimating pooled covariance based on
      an F contrast.
      """
  
      ## TODO check nipy.algorithms.statistics.models.contrast to see if rank is
      ## correctly set -- I don't think it is right now.
      print(dfnum, dfdenom)
      thresh = FDbn.ppf(pvalue, dfnum, dfdenom)
      return Image(
          np.greater(np.asarray(Fimg), thresh), Fimg.grid.copy()
      )
  
file_path: nipy/nipy/modalities/fmri/spm/model.py
imports: import numpy
  import numpy.linalg
  from scipy.stats import f
  from nipy.algorithms.statistics.models.regression import GLSModel, OLSModel
  from nipy.core.api import Image
  from nipy.modalities.fmri.fmristat import model
  from nipy.modalities.fmri.fmristat.model import OLS
  from .None import correlation, reml
label_desc: Use image node_id 1 for calling a global function with example usage: Fmask(Fimg, dfnum, dfdenom, pvalue) and returns: Image