Remove unused clearsky._is_leap_year (closes #2768)

Author: dgowdaan-cmyk

docs/sphinx/source/whatsnew/v0.15.3.rst

@@ -38,7 +38,7 @@ Requirements
 
 Maintenance
 ~~~~~~~~~~~
-
+* Removed unused internal function ``clearsky._is_leap_year`` (:issue:`2768`, :pull:`XXXX`)
 
 Contributors
 ~~~~~~~~~~~~

pvlib/clearsky.py

@@ -220,22 +220,6 @@ def lookup_linke_turbidity(time, latitude, longitude, filepath=None,
     return linke_turbidity
 
 
-def _is_leap_year(year):
-    """Determine if a year is leap year.
-
-    Parameters
-    ----------
-    year : numeric
-
-    Returns
-    -------
-    isleap : array of bools
-    """
-    isleap = ((np.mod(year, 4) == 0) &
-              ((np.mod(year, 100) != 0) | (np.mod(year, 400) == 0)))
-    return isleap
-
-
 def _interpolate_turbidity(lts, time):
     """
     Interpolated monthly Linke turbidity onto daily values.