Update.

grext/main.py

@@ -4,13 +4,16 @@ from typing import Optional
 import numpy as np
 
 from . import grassmann
+from . import fitting
 from .buffer import CircularBuffer
 
 class Extrapolator:
 
     """Class for performing Grassmann extrapolations. On initialization
     it requires the number of electrons, the number of basis functions
-    and the number of atoms of the molecule."""
+    and the number of atoms of the molecule. The number of previous
+    steps used by the extrapolator is an optional argument with default
+    value of 10."""
 
     def __init__(self, nelectrons: int, nbasis: int, natoms: int,
             nsteps: int = 10):
@@ -41,6 +44,7 @@ class Extrapolator:
 
     def guess(self, coords: np.ndarray, overlap: Optional[np.ndarray]):
         """Get a new electronic density to be used as a guess."""
+        coefficients = fitting.linear()
 
     def _crop_coeff(self, coeff) -> np.ndarray:
         """Crop the coefficient matrix to remove the virtual orbitals."""
@@ -56,13 +60,13 @@ class Extrapolator:
         """Set the tangent point."""
         self.tangent = c
 
-    def _grassmann_log(self, coeff: np.ndarray):
+    def _grassmann_log(self, coeff: np.ndarray) -> np.ndarray:
         """Map from the manifold to the tangent plane."""
         if self.tangent is not None:
             return grassmann.log(coeff, self.tangent)
         raise ValueError("Tangent point is not set.")
 
-    def _grassmann_exp(self, gamma: np.ndarray):
+    def _grassmann_exp(self, gamma: np.ndarray) -> np.ndarray:
         """Map from the tangent plane to the manifold."""
         if self.tangent is not None:
             return grassmann.exp(gamma, self.tangent)