How to use the hl7apy.core.Field function in hl7apy

def test_to_string_msh_field_v27(self):
        for v in ('2.7', '2.8', '2.8.1', '2.8.2'):
            m = Message('OML_O33', version=v)
            msh = m.msh
            self.assertEqual(msh.msh_1.to_er7(), '|')
            self.assertEqual(msh.msh_2.to_er7(), '^~\\&#')
            msh_1 = Field('MSH_1')
            msh_2 = Field('MSH_2')
            self.assertRaises(IndexError, msh_1.to_er7)
            self.assertRaises(IndexError, msh_2.to_er7)

# name with base datatype
        m = Message('RSP_K21')
        m.pid.pid_39.cwe_1 = ST(cmp_str)
        self.assertEqual(m.pid.pid_39.cwe_1.to_er7(), cmp_str)

        # value with base datatype
        m = Message('RSP_K21')
        m.pid.pid_39.cwe_1.value = ST(cmp_str)
        self.assertEqual(m.pid.pid_39.cwe_1.to_er7(), cmp_str)

        # complex datatype
        complex_cmp_str = 'xxx&yyy&zzz'

        # name
        f = Field('PID_4')
        f.cx_10 = complex_cmp_str
        self.assertEqual(f.cx_10.to_er7(), complex_cmp_str)
        self.assertEqual(len(f.cx_10.children), 3)

        # value
        f = Field('PID_4')
        f.cx_10.value = complex_cmp_str
        self.assertEqual(f.cx_10.to_er7(), complex_cmp_str)
        self.assertEqual(len(f.cx_10.children), 3)

def test_create_varies_datatype_field(self):
        f = Field('PID_1', datatype='varies')
        self.assertEqual(f.datatype, 'varies')

def test_to_string_msh_field_v27(self):
        for v in ('2.7', '2.8', '2.8.1', '2.8.2'):
            m = Message('OML_O33', version=v)
            msh = m.msh
            self.assertEqual(msh.msh_1.to_er7(), '|')
            self.assertEqual(msh.msh_2.to_er7(), '^~\\&#')
            msh_1 = Field('MSH_1')
            msh_2 = Field('MSH_2')
            self.assertRaises(IndexError, msh_1.to_er7)
            self.assertRaises(IndexError, msh_2.to_er7)

def test_to_string_msh_field(self):
        m = Message('OML_O33')
        msh = m.msh
        self.assertEqual(msh.msh_1.to_er7(), '|')
        self.assertEqual(msh.msh_2.to_er7(), '^~\\&')
        msh_1 = Field('MSH_1')
        msh_2 = Field('MSH_2')
        self.assertRaises(IndexError, msh_1.to_er7)
        self.assertRaises(IndexError, msh_2.to_er7)

def test_override_field_datatype_strict(self):
        f = Field('pid_3',  validation_level=VALIDATION_LEVEL.STRICT)
        with self.assertRaises(OperationNotAllowed):
            f.datatype = 'HD'
        self.assertRaises(OperationNotAllowed, Field, 'pid_3', datatype='HD',
                          validation_level=VALIDATION_LEVEL.STRICT)
        # in this case we are assigning the official datatype to the Field, thus no exception should be raised
        b = Field('pid_3', 'CX', validation_level=VALIDATION_LEVEL.STRICT)
        self.assertEqual(b.datatype, 'CX')

        f = Field('pid_3')
        f.datatype = 'HD'
        self.assertEqual(f.datatype, 'HD')

        f = Field('pid_3', datatype='HD')
        self.assertEqual(f.datatype, 'HD')

        # it raises an exception because the field already has some children

def test_assign_wrong_component_to_known_position(self):
        f1 = Field('pid_10', validation_level=VALIDATION_LEVEL.STRICT)
        with self.assertRaises(ChildNotValid):
            f1.ce_1 = Component('CX_1')
        f2 = Field('pid_3')
        with self.assertRaises(ChildNotValid):
            f2.cx_1 = Component('HD_1')
        f2.cx_1 = Component('CX_1')

        m = Message('RSP_K21', validation_level=VALIDATION_LEVEL.STRICT, reference=self.rsp_k21_mp)
        f = m.add_segment('QPD').add_field('QPD_3')
        with self.assertRaises(ChildNotValid):
            f.qip_1 = Component('CX_1')

        m = Message('RSP_K21', validation_level=VALIDATION_LEVEL.TOLERANT, reference=self.rsp_k21_mp)
        f = m.add_segment('QPD').add_field('QPD_3')
        with self.assertRaises(ChildNotValid):
            f.qip_1 = Component('CX_1')

def test_field_wgith_three_part_name_bug_39(self):
        """
        Tests that fields with three part name are handled correctly. See issue #39 on github
        """
        f = Field('MSH_9', version='2.3')
        f.value = 'SIU^S12'
        self.assertEqual(f.cm_msg_1.value, 'SIU')
        self.assertEqual(f.cm_msg_2.value, 'S12')

def test_create_empty_field(self):
        f = Field()
        self.assertEqual(f.classname, 'Field')
        self.assertRaises(OperationNotAllowed, Field, validation_level=VALIDATION_LEVEL.STRICT)

>>> print(unknown.to_er7())
    NUCLEAR^NELDA^W
    """
    version = _get_version(version)
    encoding_chars = _get_encoding_chars(encoding_chars, version)
    validation_level = _get_validation_level(validation_level)

    try:
        field = Field(name, version=version, validation_level=validation_level, reference=reference)
    except InvalidName:
        if force_varies:
            reference = ('leaf', None, 'varies', None, None, -1)
            field = Field(name, version=version, validation_level=validation_level, reference=reference)
        else:
            field = Field(version=version, validation_level=validation_level, reference=reference)

    if name in ('MSH_1', 'MSH_2'):
        s = SubComponent(datatype='ST', value=text, validation_level=validation_level, version=version)
        c = Component(datatype='ST', validation_level=validation_level, version=version)
        c.add(s)
        field.add(c)
    else:
        children = parse_components(text, field.datatype, version, encoding_chars, validation_level,
                                    field.structure_by_name)
        if Validator.is_tolerant(validation_level) and is_base_datatype(field.datatype, version) and \
                len(children) > 1:
            field.datatype = None
        field.children = children
    return field