diff --git a/grasp2alm/beam_cut.py b/grasp2alm/beam_cut.py
index 5e024fb..cfaad29 100644
--- a/grasp2alm/beam_cut.py
+++ b/grasp2alm/beam_cut.py
@@ -3,6 +3,7 @@
 from dataclasses import dataclass, field
 import numpy as np
 import matplotlib.pyplot as plt
+from typing import Union
 from .beam_polar import BeamPolar
 
 @dataclass
@@ -34,12 +35,13 @@ class BeamCut:
     vini: float = 0.0
     vinc: float = 0.0
     vnum: int = 0
-    c: np.ndarray = np.array([]) # TODO check is it needed variable
+    c: np.ndarray = None # TODO check is it needed variable
+
     icomp: int = 0
     icut: int = 0
     ncomp: int = 0
     ncut: int = 0
-    amp: np.ndarray = field(default_factory=lambda: np.array([]))
+    amp: np.ndarray = None
 
     def __init__(self, filepath):
         super().__init__()
@@ -76,7 +78,7 @@ def __post_init__(self):
                     break
                 data = line.split()
                 if len(data) == 7:
-                    self.vini, self.vinc, self.vnum, c, self.icomp, self.icut, self.ncomp = map(float, data)
+                    self.vini, self.vinc, self.vnum, self.c, self.icomp, self.icut, self.ncomp = map(float, data)
                     self.vnum, self.icomp, self.icut, self.ncomp = map(int, (self.vnum, self.icomp, self.icut, self.ncomp))
                     for i in range(self.vnum):
                         line = fi.readline()
diff --git a/grasp2alm/beam_grid.py b/grasp2alm/beam_grid.py
index 17615bf..54846ec 100644
--- a/grasp2alm/beam_grid.py
+++ b/grasp2alm/beam_grid.py
@@ -56,7 +56,7 @@ class BeamGrid:
     ny: int = 0
     freq: float = 0.0
     frequnit: str = ""
-    amp: np.ndarray = field(default_factory=lambda: np.array([]))
+    amp: np.ndarray = None
 
 
     def __init__(self, filepath):
diff --git a/notebooks/tutorial.ipynb b/notebooks/tutorial.ipynb
index 0f3c526..ada3cc6 100644
--- a/notebooks/tutorial.ipynb
+++ b/notebooks/tutorial.ipynb
@@ -30,12 +30,12 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 2,
+   "execution_count": 4,
    "metadata": {},
    "outputs": [],
    "source": [
-    "gridfile = \"../grasp2alm/test/beam_files/test.grd\"\n",
-    "cutfile = \"../grasp2alm/test/beam_files/test.cut\"\n",
+    "gridfile = \"../test/beam_files/test.grd\"\n",
+    "cutfile = \"../test/beam_files/test.cut\"\n",
     "grid = g2a.BeamGrid(gridfile)\n",
     "cut = g2a.BeamCut(cutfile)"
    ]
@@ -56,7 +56,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 3,
+   "execution_count": 5,
    "metadata": {},
    "outputs": [
     {
@@ -100,7 +100,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 4,
+   "execution_count": 6,
    "metadata": {},
    "outputs": [
     {
@@ -204,7 +204,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 5,
+   "execution_count": 7,
    "metadata": {},
    "outputs": [
     {
@@ -248,7 +248,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 6,
+   "execution_count": 8,
    "metadata": {},
    "outputs": [
     {
@@ -322,7 +322,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 7,
+   "execution_count": 9,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -330,11 +330,6 @@
     "calm = cmap.to_alm()"
    ]
   },
-  {
-   "cell_type": "markdown",
-   "metadata": {},
-   "source": []
-  },
   {
    "cell_type": "markdown",
    "metadata": {},
@@ -344,7 +339,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 8,
+   "execution_count": 10,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -354,7 +349,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 9,
+   "execution_count": 11,
    "metadata": {},
    "outputs": [],
    "source": [