diff --git a/requirements.txt b/requirements.txt
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+++ b/requirements.txt
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+pytest==7.3.1
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diff --git a/src/array_flatten.py b/src/array_flatten.py
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+++ b/src/array_flatten.py
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+from typing import List, Union
+
+def flatten_array(arr: List[Union[int, List]]) -> List[int]:
+    """
+    Flatten a nested list of integers into a single-level list.
+    
+    This function recursively flattens a list that may contain nested lists 
+    of integers into a single-level list of integers.
+    
+    Args:
+        arr (List[Union[int, List]]): A list that may contain integers or nested lists
+    
+    Returns:
+        List[int]: A flattened list of integers
+    
+    Raises:
+        TypeError: If the input contains non-integer and non-list elements
+    
+    Examples:
+        >>> flatten_array([1, [2, 3], 4])
+        [1, 2, 3, 4]
+        >>> flatten_array([1, [2, [3, 4]], 5])
+        [1, 2, 3, 4, 5]
+    """
+    flattened = []
+    
+    for item in arr:
+        # If the item is a list, recursively flatten it
+        if isinstance(item, list):
+            flattened.extend(flatten_array(item))
+        # If the item is an integer, add it to the flattened list
+        elif isinstance(item, int):
+            flattened.append(item)
+        else:
+            # Raise an error for non-integer and non-list elements
+            raise TypeError(f"Unsupported type in array: {type(item)}")
+    
+    return flattened
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diff --git a/tests/test_array_flatten.py b/tests/test_array_flatten.py
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+++ b/tests/test_array_flatten.py
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+import pytest
+from src.array_flatten import flatten_array
+
+def test_flatten_simple_list():
+    """Test flattening a simple list"""
+    assert flatten_array([1, 2, 3]) == [1, 2, 3]
+
+def test_flatten_nested_list():
+    """Test flattening a list with one level of nesting"""
+    assert flatten_array([1, [2, 3], 4]) == [1, 2, 3, 4]
+
+def test_flatten_deeply_nested_list():
+    """Test flattening a list with multiple levels of nesting"""
+    assert flatten_array([1, [2, [3, 4]], 5]) == [1, 2, 3, 4, 5]
+
+def test_flatten_empty_list():
+    """Test flattening an empty list"""
+    assert flatten_array([]) == []
+
+def test_flatten_list_with_empty_sublists():
+    """Test flattening a list with empty sublists"""
+    assert flatten_array([1, [], [2, []], 3]) == [1, 2, 3]
+
+def test_invalid_type_raises_error():
+    """Test that non-integer, non-list elements raise a TypeError"""
+    with pytest.raises(TypeError):
+        flatten_array([1, 2, "3"])
+
+def test_nested_invalid_type_raises_error():
+    """Test that nested invalid types also raise a TypeError"""
+    with pytest.raises(TypeError):
+        flatten_array([1, [2, "3"], 4])
+
+def test_multiple_nested_levels():
+    """Test flattening a list with multiple nested levels"""
+    assert flatten_array([1, [2, [3, [4, 5]]], 6]) == [1, 2, 3, 4, 5, 6]
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