docs: def sample_correlations(self):
          """Returns an `ExpMatrix` containing all pairwise sample correlations.
  
          Returns
          -------
          `ExpMatrix`
              The sample correlation matrix.
  
          """
          C = np.corrcoef(self.X.T)
          corr_matrix = ExpMatrix(genes=self.samples, samples=self.samples, X=C)
          return corr_matrix