Adding docstring to PolyA

sequence_extractor/polyA.py

 import numpy as np
 
 def PolyA_generator(exon):
+def PolyA_generator(exon):
+"""Appends PolyA tail.
+
+    This function appends a polyA tail on the transcript sequence based on a random selection of bases, with A defined as being in larger proportion..
+
+    Parameters
+    ----------
+    arg1 : exon
+             Transcript sequence made up of exons.
+
+    Returns
+    -------
+    fasta
+        Transcript sequence with concatenated polyA tails.
+
+
+
+    Raises
+    ------
+    TypeError
+        ValueError: PolyA tail needs to contain majority As.
+    """
+listA = ['A','T','G','C']
+        polyA = ''.join(np.random.choice(listA,250,p=[0.9,0.040,0.020,0.020]))
+        return (exon+polyA)
 	listA = ['A','T','G','C']
 	polyA = ''.join(np.random.choice(listA,250,p=[0.9,0.040,0.020,0.020]))
 	return (exon+polyA)